a.[href*="jpg"] {
color : green;
}

This will apply the style to all anchor tags which have their href tag linking to jpg images.

a.[href*="jpg"][id="nav"] {
color : green;
}

This will apply the style to all anchor tags which have their href tag linking to jpg images AND (satisfy both requirements) which have id as “nav”.

Related posts:

1. Use .htaccess to rewrite/redirect requests

For example, if there an unordered list tag above a paragraph tag. The list tag is assigned with the bottom margin of 20 pixels and the paragraph is assigned a value of  top margin as 20 pixels.

<ul style="margin-bottom: 20px;"><li><li></ul>

<p style="margin-bottom: 10px;"></p>

Then, a general perception would be that the browser adds them up and puts 30 pixels of white space between the paragraph and the list. But this doesn’t happen. The browser applies the larger (20px here) of the two. And you see only 20px wide white space.

Workaround: Use padding on one tag along with margin on another. 

Note: left, right margins, margins between flating elements and margins between absolutely/relatively positioned elements, don’t behave this way (colliding).

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1. CSS font-size property not working in Internet Explorer
2. How to know memory used by current running tasks on Windows

Table_1

Table_2

then to show the product names with their price, we can write an SQL statement (Inner Join) like this,

SELECT a.product_name, b.product_price FROM Table_1 a, Table_2 WHERE a.product_id=b.product_id;

This would give you the result as,

Related posts:

1. Common mistakes and points to remember in MySQL

#!/usr/bin/perl
use strict;
use warnings;

my $string = 'needle in the haystack. needle again. needle';
my $find_me = 'needle';
my $offset = 0;
my $result = index($string, $find_me, $offset);

while ($result != -1) {
   print "Found $find_me at $result\n";
   $offset = $result + 1;
   $result = index($string, $find_me, $offset);
}

Related posts:

1. Greedy Search in Perl Regular Expressions
2. Alter Regular Expression Match Position in Perl
3. How to know if document exists on a URL in perl

Try www.bing-vs-google.com

bing-vs-google

Interesting?

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$var = 'some_url?id=1&number=2&name=Peter&address=someaddress';

In the above string if you only want to capture the value of “id” (i.e. 1) and you use this regex

$var =~ /\?(.*)=(.*)\&/ ;

it will not work as expected. $1 would have this

id=1&number=2&name

(.*) tries to capture as much matching content as possible. In other words it is greedy (wants to have more and more). But of-course only the content which matches the pattern.

If you want to capture id=1 only in $1 and $2 respectively you have to refrain the greed of regex by using ? (question mark) like this,

$var =~ /\?(.*?)=(.*?)\&/ ;
print "$1 and $2\n";

it would print,

id and 1

You can use (.+) in place of (.*) to make sure that it matches only when some character there for sure, on eor more times.

$var =~ /\?(.+?)=(.+?)\&/ ;

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2. How to know if document exists on a URL in perl
3. How to get elements from one array but not in another array

We can send mail in UNIX using “mail” command. Syntax is as follows,

mail -s "Subject" -c "any_cc_email_id" -b "any_bc_email_id" "comma_separated_To_email_id"

But the above syntax is used when we are typing the message body at command-line itself.

If we want to use the body text from some variable or from some pipe (|) we need to use following syntax,

echo $message | mail -s "Subject" -c "any_cc_email_id" -b "any_bc_email_id" "comma_separated_To_email_id"

e.g.,

echo "Hi Friend, this is mail body" | mail -s "Hi Friend" "info@expertsguide.info,abcd@gmail.com"

If we want to get the message body from a file rather than from a variable, we need to following syntax

mail -s "Subject" -c "any_cc_email_id" -b "any_bc_email_id" "comma_separated_To_email_id" < file.txt

e.g.,

mail -s "Hi Friend" "info@expertsguide.info,abcd@gmail.com" < myfile.log

Lot of programmers ask about how to send this mail to multiple users. Please note that they need to put comma separated email ids and not space separated ones in the above syntax (as I have already shown).

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3. HTTP Authentication in URL not working in IE

use LWP::Simple;
$URL='http://www.expertsguide.info/';
if (head($URL))
{
   print '$URL exists' ;
}
else
{
   print 'URL does not contain anything';
}

head() function returns much more information eg,  Content-type, document length, last modified time, expiry date and server name. Capture that using,

my @headers = head $URL;
print join "\n", @headers;

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2. New Text Document on right click menu missing
3. How to access elements having some Class using Javascript?

If you open the command prompt on windows (Start->Run->cmd  and Press Enter), it opens a command prompt. Type “tasklist” and press enter. It gives a long table with 5 columns (Image Name, PID,  Session Name, Session #, Mem Usage)

First column “Image Name” shows the executable running corresponding to a task or process, e.g., for Mozilla Firefox it should be “firefox.exe”, second column shows it’s process Id (PID) and the last one memory used (Mem Usage)

If we want to get the result only for processes using memory larger than 50000 KB we can use this command,

tasklist /FI "MEMUSAGE gt 50000" /FO TABLE

where,
/FI denotes the field-name input identifier (any one of the five fields)
/FO denotes Field output format (this can be either TABLE,LIST or CSV)

Similary,
If we want to get the memory usage of a process with it’s id use this

tasklist /FI "PID eq 4568" /FO LIST

This can be used in various scripts on windows or by programming languages like Perl, PHP, C, etc. running on windows.

To get the syntax and help text use this,

tasklist /?

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1. how to set or change a default printer on windows?
2. Common mistakes and points to remember in MySQL

1. For SELECT, SHOW, DESCRIBE, EXPLAIN and other statements returning resultset, mysql_query() returns a resource on success, or FALSE on error. For other type of SQL statements like INSERT, UPDATE, DELETE, DROP, etc, mysql_query() returns TRUE on success or FALSE on error (i.e. boolean result and not a resource). Use mysql_num_rows() to find out how many rows were returned for a SELECT statement or mysql_affected_rows() to find out how many rows were affected by a DELETE, INSERT, REPLACE, or UPDATE statement.

$sql = "UPDATE tablename SET id='123'";
$result = mysql_query($sql) or die("Error: Cannot execute SQL : ".mysql_error() );
if($result !==  false) // correct, context check
{
    $num_rows = mysql_num_rows($result);      //incorrect   rather use mysql_affected_rows()
    while ($row = mysql_fetch_assoc($result))   //incorrect for UPDATE statement
    { }
}

The returned result resource (by SELECT, SHOW, DESCRIBE, EXPLAIN etc) should be passed to mysql_fetch_array(), and other functions for dealing with result tables, to access the returned data.

mysql_query() will also fail and return FALSE if the user does not have permission to access the table(s) referenced by the query.

A resource can be checked by the following,

$db_link = @mysql_connect('localhost', 'mysql_user', 'mysql_pass');
if (!is_resource($db_link))  {
   die('Can not connect : ' . mysql_error());
}

mysql_free_result() will free all memory occupied by the resultset.

mysql_free_result() only needs to be called if you are concerned about how much memory is being used for queries that return large result sets. All associated result memory is automatically freed at the end of the script’s execution. Using this function may actually increase the amount of memory used (use it when you know the resultset is really large).  Use memory_get_usage() at the end of the script to see the memory usage by MySQL.

2. We sometimes pass the user inputs directly to the SQL statements which is a big security threat. Sanitize the user inputs before passing them to SQLs.

$query = sprintf( 'SELECT id, name FROM People WHERE name = IN (%s)',
implode(',', array_map( 'mysql_real_escape_string', $names_array )) );

function my_real_escape_string($string)
{
   if (get_magic_quotes_gpc())
      $string = stripslashes($string); //if magic quotes are enabled, it automatically prepends backslash
   return mysql_real_escape_string($string);
}

3. Number of rows affected is 0 (zero) if same value is being updated using UPDATE in MySQL (actually it doesn’t update if value is same) hence creating a wrong impression that our update statement failed and giving error. So proper check should be done before dumping an error.
Also, remember the parameter passed to mysql_affected_rows() is a link resource NOT a resultset.
While that to mysql_num_rows() is a resutset.

4. Instead of executing SQL commands in a loop try executing it once only and store the output in some variavle or array. This increases efficiency and reduces execution time.
Wrong Approach,

$res = myql_query($first_query) or die ("Error 1");
while($row = mysql_fetch_row($res) )
{   //faster than mysql_fetch_assoc()
    $second_query = "select name from table where id= $row[0]";
    $res = myql_query($second_query) or die ("Error 2");
    while($row2 = mysql_fetch_row($res) )
    {
       ....
    }
}

Right Approach,

$str="";
$res = myql_query($first_query) or die ("Error 1");
while($row = mysql_fetch_row($res) )
{   //faster than mysql_fetch_assoc()
    $str .= $row[0].',';
}
//remove last comma
$str = (substr($str,-1) == ',') ? substr($str, 0, -1) : $str;

$second_query = "select name from table where id IN ($str)";
$res = myql_query($second_query) or die ("Error 2");
while($row2 = mysql_fetch_row($res) )
{
       ....
}

5. Always fetch definite columns from SQL and try to avoid * in select statements. It unnecessarily fetches all the columns which might not be needed.

SELECT * from table            //bad
SELECT id,name from table   //good

6. Open connections time out after a default setting (in MySQL conf file). But still you should take the honour of closing the connections once you are done with it. If you don’t, PHP will close it on exiting.

Useful SQLs to check performance:
a. Query “SHOW PROCESSLIST” shows which processes in MySQL are currently running.
b. Query “SHOW STATUS” shows the current number of connections.

Related posts:

1. Sanitize User Input with MySQL
2. How to optimize PHP code

Put the below lines in a plain text file. Upload that to your home directory on your web-server and rename it as “.htaccess”. This would allow an upload of upto 20 MB file sizes.

php_value upload_max_filesize 20M
php_value post_max_size 20M
php_value max_execution_time 200
php_value max_input_time 200

Enjoy uploading !

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1. How to parse PHP in html pages
2. Stop indexing files in a directory using .htaccess
3. Use .htaccess to rewrite/redirect requests

Sometimes we want to test our code for efficiency and execution time by comparing it with other code. Here’s how you can compare two code blocks in PHP and decide which one is faster (helps in optimization of code).

$str = '1,2,3,4,';   //we will trim the trailing comma

$time = microtime(); $micro1 = explode(' ', $time);
echo "Started at $time\n";    //Note the starting time.

$str1 = (substr($str,-1) == ',') ? substr($str, 0, -1) : $str;

$time = microtime(); $micro2 = explode(' ', $time);
echo "Took ", bcsub($micro2[1],$micro1[1]), bcsub($micro2[0],$micro1[0],6)," secs\n";

$str2 = preg_replace("/,*$/", '', $str);

$time = microtime(); $micro3 = explode(' ', $time);
echo "Took ", bcsub($micro3[1],$micro2[1]), bcsub($micro3[0],$micro2[0],6)," secs\n";

Output:
It ran it a few times on command-line on my local computer and it gave,

D:\>php New9.php
Started at 0.59481000 1283787551
Took 00.000610 secs
Took 00.001064 secs

D:\>php New9.php
Started at 0.01657800 1283787594
Took 00.000658 secs
Took 00.001177 secs

D:\>php New9.php
Started at 0.29726000 1283787644
Took 00.000390 secs
Took 00.000557 secs

D:\>php New9.php
Started at 0.57921400 1283787650
Took 00.000614 secs
Took 00.001060 secs

D:\>php New9.php
Started at 0.68782700 1283787653
Took 00.000372 secs
Took 00.000497 secs

Related posts:

1. How to optimize PHP code
2. How to remove last comma from a string in PHP?

for($i=0; $i<count($array); $i++)  //not good

If the array length (max iterations for the loop) is not changing, calculated it outside loop body or in the initialization portion (before first semicolon). It does not get calculated in every iteration and hence reduces load.

$length = count($array);
for($i=0; $i<$length; $i++) //good

or

for($i=0, $length=count($array); $i<$length; $i++) //good (it is same as above)

2) When using arrays or MySQL result objects use “while” or “foreach” loop. This would save us extra step of incrementing/decrementing the counter in every iteration, eg,

while ($row = mysql_fetch_assoc($result)) {
    echo $row["userid"];
}
mysql_free_result($result);  // release the memory

3) Try to avoid regular expression engine overhead wherever possible.
To search a substring, PHP function strpos() is fastest, then preg_match() and then ereg().
In the same way, PHP function str_replace() is faster than preg_replace(), which is faster than ereg_replace().

4) Use “switch” in case of multiple “if”s and “else”s. Keep most frequently occuring cases on top in the switch body. If some common cases are still there in the default section, explicitly define them at the top to prevent condition checks of multiple cases. If case condition matches at the top itself, execution comes out immediately, hence program runs faster.

5) Release memory by unsetting variables (PHP function unset(); ) which are no more used. Do it especially for resources and large arrays. For releasing MySQL resources use mysql_free_result(), close the DB connection as soon as you are done with it.

6) Use multiple parameters of echo instead of string concatenation and then echoing it, eg,

echo $var1.$var2.$var3;  //not good
echo $var1, $var2, $var3;  //good

7) Use single quote instead of double quotes when there is no varible to be printed by echo.

echo "Hello World"; //not good
echo 'Hello World'; //good
echo 'Hello ', $username, ' welcome back';

8 ) Use PHP function isset() to check the existence of a variable, before using this variable in any condition or calculation.

if ( strcmp($_POST['id'], '12345')==0  ) //not good
//if id is not set there's no point in comparision
if (isset($_POST['id']) && ( strcmp($_POST['id'], '12345')==0 ) ) //good

9) mt_rand() is four times faster than rand().
If you need to create random numbers, with or without the range, use mt_rand() instead of rand()

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1. Usefull PHP array functions
2. How to get elements from one array but not in another array
3. Sanitize User Input with MySQL

The following URL syntax may not work in Internet Explorer or in Windows Explorer,
http(s)://username:password@mydomain.com

Reason:
Such URL syntax is used to automatically send username/password to a Web site which requires basic authentication.
A hacker may exploit this nomenclature and make a hyperlink which looks like opening a legal/intended Web site but in reality opens a another, e.g., http://www.expertsguide.info@example.com doesn’t open http://www.expertsguide.info which you would think should, rather opens http://example.com

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If you have suffered the same, no worries, here’s the solution for Windows XP.

Put this registry entry into a plain text document and name it “something.reg”. Note, extension .reg is important here. Save it and double click it. It asks you to modify the registry entry, say Yes and successfully done prompt should appear. We are done now. Restart your computer and see if it (right click->New->TEXT Document) is there.

Alternatively you can download this file from here, change the extension (remove .txt) and double click it.

Windows Registry Editor Version 5.00

[HKEY_CLASSES_ROOT\.txt]
“Content Type”=”text/plain”
@=”txtfile”
“PerceivedType”=”text”

[HKEY_CLASSES_ROOT\.txt\OpenWithList]

[HKEY_CLASSES_ROOT\.txt\PersistentHandler]
@=”{5e941d80-bf96-11cd-b579-08002b30bfeb}”

[HKEY_CLASSES_ROOT\.txt\shell]

[HKEY_CLASSES_ROOT\.txt\shell\open]

[HKEY_CLASSES_ROOT\.txt\shell\open\command]
@=”notepad.exe %1″

[HKEY_CLASSES_ROOT\.txt\ShellNew]
“NullFile”=”"

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Sometimes we do not want to show all the files in a directory (which by default is a behavior of web servers).
That can be done using htaccess file.
Though there’s a simple solution to this, put an index.html file showing a decent message “Not authorized to access this”. But that will have little control over management.

What if we want to have more control and do it at the initial stage only?
Use .htaccess file.

Put this in your htaccess file

IndexIgnore *

here * (asterisk) matches all the files so none would be displayed.

If you do not want to show .css or .conf or .php or .sh files only and let other files being shown, then,

IndexIgnore *.css
IndexIgnore *.php
IndexIgnore *.sh
IndexIgnore *.conf

or in a single line

IndexIgnore *.css *.php *.conf *.sh

This can be made to work for relative paths also, if you want to put all your htaccess statements in a single file at root level (recommended)

IndexIgnore /common-files/scripts/*

To make some file like “myfile.html” your default file (instead of index.html) which opens when a user enters a URL to access some directory, then use,

DirectoryIndex myfile.html

You can specify more than one file names, in case first is not found then immediate next one would be opened.

DirectoryIndex myfile_1.html myfile_2.html

On the contrary, if you want to show file index under a directory (opposite of stopping index) then use this,

Options +Indexes

Secure your files from accidental display to the users,

<Files ".htaccess">
    Order Deny,Allow
    Deny from all
    Allow from 122.255.43.3
</Files>

Use regular expressions (using ~) to specify file names (to secure files other than .htaccess)

<Files ~ "\.(gif|jpe?g|png)$">
   Order Deny,Allow
   Deny from all
  Allow from 122.255.43.3
</Files>

or

<FilesMatch "\.(gif|jpe?g|png)$">

Keep checking this article for more updates.

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2. Use .htaccess to rewrite/redirect requests
3. How to parse PHP in html pages

Use htaccess file.
this is run by server and ensured by the server that the rules written in it are enforced.

On the other hand, robots.txt file is just a guideline file. Robots are not bound to follow it.

To ensure denial of all requests for the restricted directory, put the following in the .htaccess file (keep it in the same directory),

deny from all

Allow access from one IP only and deny others,

order deny, allow
deny from all
allow from 255.255.12.34
ErrorDocument 403 errordoc.html

Allow access from a range of IPs (may be a LAN or a country),

order deny, allow
deny from all
allow from 255.255.0

Deny access from certain IP (e.g. a bot),

order allow, deny
deny from 255.255.123.456
allow from all

Block a bad bot

RewriteEngine on
RewriteCond %{HTTP_USER_AGENT} ^dirtybot
RewriteRule ^(.*)$ http://emptypage/

or use [F] to send Forbidden signal
RewriteRule .* – [F]

Block more that one bots

RewriteEngine on
RewriteCond %{HTTP_USER_AGENT} ^dirtybot [OR]
RewriteCond %{HTTP_USER_AGENT} ^badCrawler [OR]
RewriteCond %{HTTP_USER_AGENT} ^fakeOne
RewriteRule ^(.*)$ http://emptypage/

Deny more than one IPs or bot IPs

order allow,deny
deny from 255.255.123.456
deny from 123.255.123.456
deny from 456.255.123.456
allow from all

Deny more than one IPs or bot IPs ranges (may be countries)

order allow,deny
deny from 255.255.
deny from 123.456.
allow from all

Block particular ISPs,

order allow,deny
deny from this-bad-isp.com
deny from subdomain.bad-isp.com
allow from all

Block some referers or websites from accessing your content like images or css or js files

RewriteEngine on
RewriteCond %{HTTP_REFERER} ^http://.*somebadforum\.com [NC,OR]
RewriteCond %{HTTP_REFERER} ^http://.*example\.com [NC,OR]
RewriteCond %{HTTP_REFERER} ^http://.*lastexample\.com [NC]
RewriteRule .* - [F]

Keep checking regular updates on http://www.expertsguide.info/

Related posts:

1. Use .htaccess to rewrite/redirect requests

File, called as .htaccess, can be used to rewrite URLs apart from doing other stuffs like application handlers etc.

We can do some potent manipulations with our links, like,

• Transforming long URL’s into short, easy to remember URLs
• Transforming URLs having in-comprehensive query strings like “filename?id=carnivores&cat=animals” into  human readable URLs like “livingthings/animals/carnivores”
• Redirect missing pages. Instead of showing  frustrating  messages like “401 Page Not Found” you can show your users a neat html pages showing a humble message like “Your request seems to be having wrong structure. Please check your URL“. Or “We are under maintenance. Please be back after some time“.
• Preventing hot-linking. Hot linking is, a third party using your servers bandwidth to access some stuff from your server directly eg images, css, javascript etc.
• Performing automatic language translation (keeping all language files under one directory), etc.

Lets start writing our .htaccess file. We should put two lines (Options +FollowSymlinks and  RewriteEngine on) in almost all .htaccess files to start the writing engine (details out of scope).  I will skip these two lines in my examples, please remember to have them in your file. The third line specifies which directory to start from (make base directory). Note: In case you are putting htaccess file in some sub directory then RewriteBase should be written to point to that sub-directory else rewritten URLs (targets) will be relative to home directory of the domain.

1) How to rewrite http://www.host.com/somefile.html to http://www.host.com/somefile.php

Options +FollowSymlinks
RewriteEngine on
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^(.*)\.html$ $1.php

Forward slash (/) here means home directory of http://www.host.com/) (usually public_html)
Therefore our rewrite rules would match only filenames & paths which are just after http://www.host.com/ (here somefile.html)

^, (.*),  $ and $1 are all regular expression special characters having special meaning e.g, ^ is to match the start of the string (it is start anchor), similarly $ is end anchor. Do not get confused with $1, it is not an anchor. It carries the back-referenced data captured with the parentheses “(” and “)”. A dot “.” matches any character and an asterisk following this dot means zero or more characters. A dot preceded by a back slash \. matches the literal dot (and not any character). For more info please refer regular expression tutorials.

2) How to rewrite all language files to a language directory, say, http://www.host.com/file.html to http://www.host.com/french/file.html

RewriteRule ^(.*)\.html$ french/$1.html

3) How to permanently redirect old URLs to new ones (to secure old page ranks)

RewriteCond %{HTTP_HOST} ^olddomain\.com$ [NC]
RewriteRule ^(.*)$ http://www.mynewdomain.com/$1 [R=301,L]

Here [NC] refers to case insensitive match and R=301 gives the HTTP Response to the client as “Permanently moved” to new URL.
It will tell crawlers not to discard old URLs from their index and drop the page rank rather replace old ones with new ones.
or

Redirect permanent /oldhtmlfile.htm http://your-domain.com/newhtmlfile.htm

This way we can either strip www. from our domain (or add it, if you want) to put away ambiguity (between http://domain.com and http://www.domain.com) for crawlers and maintain a uniform linkage with external websites. For crawlers both are different entities.

To strip www.

RewriteCond %{HTTP_HOST} ^www\.mydomain\.com
RewriteRule ^(.*)$ http://mydomain.com/$1 [R=permanent,L]

To add www.

RewriteCond %{HTTP_HOST} ^mydomain\.com
RewriteRule ^(.*)$ http://www.mydomain.com/$1 [R=permanent,L]

Note: Moved permanently response code can also be served using PHP but that is not as good as doing by .htaccess file.

<?php
Header( "HTTP/1.1 301 Moved Permanently" );
Header( "Location: http://www.mydomain.com" );
?>

4) How to catch query strings (?var=value&var2=value2 etc) to readable ones, say, http://www.host.com/file.php?cat=123 to http://www.host.com/file.php/category/123

RewriteCond %{QUERY_STRING} cat=(.*)
RewriteRule ^file.php.* /file.php/category/%1 [R]

This can be used to redirect (not only rewrite) a user to readable URL. [R] handles redirection. %{QUERY_STRING} a global variable, contains the whole query string. This can be used to support some old URL patterns (backward compatibility). Though the reverse of it would be used to show and store the human readable URLs while at server you still process them with old functionality, eg. your users remember and write URL like file/category/carnivores  while you still process them with file.php?id=123

RewriteRule ^file/catogory/canivores/ file.php?id=123

Stop hotlinking of your images with,

RewriteEngine On
RewriteCond %{HTTP_REFERER} !^http://(.+\.)?host\.com/ [NC]
RewriteCond %{HTTP_REFERER} !^$
RewriteRule .*\.(jpe?g|gif|bmp|png)$ http://hpst.com/img/empty.gif [L]

%{HTTP_REFERER} contains the name of the refereeing website (eg http://otherhost.com). [NC] means case insensitive match, [L] means last (end up) the conditions rule here (to start another brand new rule, in case).

5) You can create some Not found error message pages.

ErrorDocument 401 /my-401-page.php

In this case if anybody requests a page which is not there on the server, s/he would be presented my-401-page.php, which can do some logging task also.

6) Limit the number of simultaneous connections to a directory or whole website (homepage) by,

MaxClients 100

7) In case of error, you can show your users an email of system administrator

ServerAdmin  admin@mydomain.com

How to debug rewrite rules in htaccess file?

a) Mostly, the problem could be that AllowOverride is not set to allow configuration directives.
You should make sure an AllowOverride None is not in effect for the file scope in question by putting garbage in your .htaccess file and reload. If a server error is not generated, then you almost certainly have AllowOverride None in effect.

b) Check the apache error log file (check through cpanel) at the sever.

c) Use the [R] option (which redirects the browser) to redirect the rewritten URL into the browser’s address bar. This URL can be appended with the matched back-references. Hence we get the regular expression matched strings in URLs e.g.,

RewriteEngine On
RewriteRule ^(.*)$ /file.php/category/match=$1 [R]

It will paste /file.php/category/match=”matched value here” in the address bar.

d) Close all instances of the browser while debugging.

Keep checking this article for more updates.

Related posts:

1. How to parse PHP in html pages

You can register here and put up your solutions also. It’s all free.

You can find here, time to time, various tips and tricks related to the above discussed topics. They would be published by the administrator of this site and will be open to discussion.

Happy Programming!

Administrator,
ExpertsGuide.info
info@expertsguide.info

<?php
$xml = <<<EOT
<?xml version="1.0" encoding="UTF-8"?>
<entry xmlns="http://www.w3.org/2005/Atom" xmlns:other="http://other.w3.org/other" >
        <id>uYG7-sPwjFg</id>
        <published>2009-05-17T18:29:31.000Z</published>
</entry>
EOT;
$doc = new DOMDocument;
$doc->loadXML($xml);
$xpath =  DOMXPath($doc);
$xpath->registerNamespace('atom', "http://www.w3.org/2005/Atom");

$xpath_str = '//atom:entry/atom:published/text()';

$entries = $xpath->evaluate($xpath_str);

print $entries->item(0)->nodeValue ."\n";

?>

You can work with HTML also

<?php
$file = "htmlfilename.html";
$doc = new DOMDocument();    //DOM Object (XML/HTML)
$doc->loadHTMLFile($file);
$xpath = new DOMXpath($doc); //XPATH Object
//$elements = $xpath->query("//*[@id]");  //for everything with an id
//$elements = $xpath->query("/html/body/div[@id='yourTagIdHere']");  //for node data in a selected id
$elements = $xpath->query("*/div[@id='yourTagIdHere']"); // same as above with wildcard

if (!is_null($elements)) {         // before entring into the loop check if something is there
  foreach ($elements as $element) {
    echo "<br/>[". $element->nodeName. "]";

    $nodes = $element->childNodes;
    foreach ($nodes as $node) {
      echo $node->nodeValue. "\n";
    }
  }
}
?>

Another simple way for XML (no hardcoding) is,

<?php
function list_xml($str) {
  $root = simplexml_load_string($str);
  list_node($root);
}

function list_node($node) {
  foreach ($node as $element) {
    echo $element. "\n";
    if ($element->children()) {
      echo "<br/>";
      list_node($element);
    }
  }
}
?>

Another one, simple but with hardcoding. Be careful using nested SimpleXML objects in double quoted strings, as they might not work as expected, you might need a curly brace to make them work.

<?php
$xmlstring = '<root><node>123</node><foo><bar>456</bar></foo></root>'; 

$root = simplexml_load_string($xmlstring); 

echo "Node is: $root->node"; // Works: Node is 123
echo "Bar is: $root->foo->bar"; // Doesn't work, outputs: Bar is: ->bar  (use curly brackets to fix)
echo "Bar is: {$root->foo->bar}"; // Works: Bar is 456 

?>

Related posts:

1. How to parse PHP in html pages
2. How to get elements from one array but not in another array
3. Access Form objects in case of multiple forms

Lets create a simple AJAX implemented webpage. and see how it works.

Create an HTML file named ajax.html. Put the following code in it.

<html>
<head>
<script>

function submitForm(url, str)
{
 var xmlhttp;
 xmlhttp=GetXmlHttpObject();
 if (xmlhttp==null)
 {
   alert ("Your browser does not support XMLHTTP!");
   return;
 }
 url=url+"?"+str;
 url=url+"&sid="+Math.random();   //to prevent the server from using a cached file
 xmlhttp.onreadystatechange=function() {
 if (xmlhttp.readyState==4 && xmlhttp.status==200)
 {
    document.getElementById('fruitresult').innerHTML = xmlhttp.responseText;
 }

 xmlhttp.open("GET",url,true);
 xmlhttp.send(null);
}

function GetXmlHttpObject()
{
/*
 try {  xhr = new ActiveXObject('Msxml2.XMLHTTP');   }
 catch (e)
 {
   try {   xhr = new ActiveXObject('Microsoft.XMLHTTP');    }
   catch (e2)
   {
     try {  xhr = new XMLHttpRequest();     }
     catch (e3) {  xhr = false;   }
   }
 }
*/
if (window.XMLHttpRequest)     // code for IE7+, Firefox, Chrome, Opera, Safari
  return new XMLHttpRequest();

if (window.ActiveXObject)     // code for IE6, IE5
  return new ActiveXObject("Microsoft.XMLHTTP");

  return null;
}
</script>
</head>

<body>
<div id="fruitresult"></div>
<FORM method="POST" name="ajax" action="">
<INPUT type="BUTTON" value="Submit"  ONCLICK="submitForm('script.php','fruit=1'); return false;">
</FORM>
</body>
</html>

Create a PHP file and save in the same directory where ajax.html is placed. Name this PHP script script.php (if you change the name you’ll have to change it in the submitForm function also)

<?php
$fruits = Array(1=>"Apple", 2=>"Banan", 3=>"Orange");
if(isset($_REQUEST['fruit']))
  echo $fruits[$_REQUEST['fruit']];
else
  echo "Sorry";
?>

Note: I have used an anonymous function in onreadystatechange event and created my xmlhttp object local (not global).
This is relly important as you might have problems in case you have made multiple calls to the same ajax file from a single HTML page.

Related posts:

1. How to access elements having some Class using Javascript?
2. How to show or hide text using javascript?

This can be done using .htaccess file in the directory where you want all your .html files to be treated as php while still showing .html in the address bar.

Create a simple text file.  Put the following code in that file.

RemoveHandler .html .htm
AddType application/x-httpd-php .php .htm .html

Save it and name it as “.htaccess” (on windows you might get problems in saving since it starts with a dot, in that case save it with any name, upload to server and then rename it) .
Upload it to your web server to your WWW root or the directory where you want this functionality.

Now lets try if it works or not.

Create a test html file, name it something lie test.html
Yes, extension should be .html
Put some php code in the html (something like below)

<html><body>
<?php echo "Success, this is from PHP code inside HTML";  ?>
</body></html>

Upload this html file (test.html) also to your web server (under the directory where you placed .htaccess ).
Open this file in any browser.
If you get the message “Success, this is from PHP code inside HTML”, time to cheer.

Keep checking this article for more updates.

Time out can be implemented in various ways in PHP e.g. by setting proper HTPP headers,  cURL options, PHP ini options, stream context options etc.

Method 1, using cURL timeout,

<?php
$url = 'http://www.example.com';
$text = content_from_curl($url);

function content_from_curl($url)
{
   $content = false;     // we will populate this with the downloaded content, if we get, else return false
   $curl = curl_init();
   curl_setopt($curl, CURLOPT_URL, $url);
   curl_setopt($curl, CURLOPT_USERAGENT, "Mozilla/4.0 (compatible; MSIE 5.01; Windows NT 5.0)");
   curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1);
   curl_setopt($curl, CURLOPT_TIMEOUT, 2);
   curl_setopt($curl, CURLOPT_CONNECTTIMEOUT, 2);

   if( ( $content = curl_exec($curl) ) === false )   {         //failure
      echo 'cURL error: ' . curl_error($ch);
   }
   else {
      //success
   }
   curl_close($curl);        // close the connection
   return $content;
}
?>

Method 2, altering PHP ini option  default_socket_timeout ,

As of PHP 5.2.1 you can set the  “timeout” context option and pass the context to file_get_contents()

Note: Other time options  like execution time and input time would have no effect.

<?php
ini_set('default_socket_timeout', 10);
$url = "http://example.com/";
if( file_get_contents( urlencode($url) ) === false ) {
   // failure
} else {
   // success
}
?>

Method 3,

By setting timeout in stream context (stream_context_create) without messing with ini values

<?php
$timeout = 6;  //seconds
$options = array(
                  'http'=>array(
                                 'method'=>"GET",
                                 'header'=>"Accept-language: en\r\n",
                                 'timeout' => $timeout )  );
$context = stream_context_create($options);
if( file_get_contents( urlencode($url), 0, $context) === false )  {
    // failure
} else {
    // success
}
?>

Method 4, using stream_set_timeout in sockets

<?php
$fp = fsockopen("www.example.com", 80);
if (!$fp) {
   echo "Unable to open\n";
}
else {
   fwrite($fp, "GET / HTTP/1.0\r\n\r\n");
   stream_set_timeout($fp, 2);
   $res = fread($fp, 2000);
   $info = stream_get_meta_data($fp);
   fclose($fp);

  if ($info['timed_out']) {
     echo 'Connection timed out!';
  }
  else {
     echo $res;
  }
}
?>

On the contrary, what if you want to increase the execution time of the script in PHP?
set_time_limit() function can be called for this. When called, set_time_limit() restarts the timeout counter from zero.
In other words, if the timeout is the default 30 seconds, and 25 seconds into script execution a call such as set_time_limit(20) is made, the script will run for a total of 45 seconds before timing out.

Keep checking this article for more updates.

Related posts:

1. How to know if a file exists on the web or not, in PHP?

font-size: small

or

font-size: medium

In mozilla firefox, it works fine.

Workaround:

Use em to specify the font size e.g.,

<style  type="text/css">
body {font-size: 0.75em;}
</style>

Inheritance can cause problems, for nested tags, when em or % sizing of the text is used. For example, if you create a style like

ul {font-size: 75%;}

then a nested list (another ul tag inside ancestor ul) is set to 75% of 75%, making the text in the inner ul smaller than the rest of the list text.

Workaround for this is, create an additional descendent selector style

ul ul {font-size:100%;}

and put it after the earlier style. Hence there would two styles (or may be more as per the nesting),

ul {font-size:75%;}
ul ul {font-size:100%;}

IE6 and earlier sometimes have problems displaying text when ony em units are used. To cope with this, there are two ways,

1) Either stick with percentage values like

font-size: 100%;}

or
2) Set the font size for the body of the page to percentage and then use em to size other text.

Related posts:

1. Button tag inside anchor not working in IE

<a href="http://www.expertsguide.info/"><button type="button">Click Me to go to Experts Guide</button></a>

I works well in Mozilla Firefox but in Internet Explorer (IE) nothing happens on clicking it.

Workaround:

Put some javascript event inside onclick event handler. Redirect (or open a new window) in javascript to required URL.

 <a href="http://www.expertsguide.info/"><button type="button" onclick="window.open('http://www.expertsguide.info/')">Click Me to go to Experts Guide</button></a>

or to open the URL in the same window,

 <a href="http://www.expertsguide.info/"><button type="button" onclick="window.location('http://www.expertsguide.info/')">Click Me to go to Experts Guide</button></a>

It should work in Mozilla Firefox as well as Internet Explorer (IE).

Related posts:

1. Access Form objects in case of multiple forms
2. How to access elements having some Class using Javascript?
3. how to set or change a default printer on windows?

Or, in other words, how to get elements from one array minus elements from another array.

The task can be simplified and made efficient (less loops and less iterations) by creating a hash (associative array) from one array elements and then matching all the elements of the other array one by one.  Example,

#!/usr/bin/perl -w

@content = (1,2,3,4,5,6,7,8,9,'a','b','c','d','e');
@alphabets = ('a','b','c','d','e','f','g','h');

# create a hash with elements of @alphabets as keys and assign them a value 1
%alpha_hash =();
foreach my $alpha (@alphabets)
{
   $alpha_hash{$alpha} = 1;
}

foreach $elem (@content)
{
    unless ($alpha_hash{$elem}) # it's not in %alpha_hash, so this is what we need
    {     
        print $elem."\n";          #it is the one not present in $alphabets 
    }
}

Instead of printing the $elem we can store it in some array, suppose @result, then this array can be visualized to be subtraction of the two.

@result = @content – @alphabets

Related posts:

1. Usefull PHP array functions
2. How to access elements having some Class using Javascript?

It can be achieved by first fetching all the div tags (or whichever you want) using function getElementsByTagName()
and then check their class name using another function className().  
It gives us more flexibility apart from getElementsByID() and getElementsByName().

<head>
<script type="text/javascript">
var allDivs = new Array();

// pass parameter "classval" the classname you want to manipulate
function getElementsByClass(classval)
{
  //Populate the array with all the div tags in the document
  allDivs = document.getElementsByTagName('div');

  for (var i=0; i<allDivs.length; i++)
  {
    var obj = allDivs[i];
    //if allDivs[i].className is null it will not go to second part of the if condition
    if ( (obj.className) && (obj.className == classval) )
    {     
      //do whatever you wish to this class
      if (obj.style.display == "none")    //check if already hidden, if yes make it appear
           obj.style.display = "";
      else
           obj.style.display = "none";    //if already appearing then hide here   
    }
  }
}
</script>
</head>
<body>
<a href="#" onclick="javascript:getElementsByClass('myclass') ; return false;">Click here</a>
<div>
<div class='myclass'>PHP</div>
<div class='myclass'>Javascript</div>
<div class='myclass'>Perl</div>
<div class='myclass'>AJAX</div>
<div class='myclass'>HTML</div>
<div class='myclass'>MySQL</div>
</div>
</body>

Related posts:

1. How to show or hide text using javascript?
2. Access Form objects in case of multiple forms

Demo html page to show/hide text using javascript.

Related posts:

1. Access Form objects in case of multiple forms

A few methods are described here and listed in the order of increasing execution time (faster listed first),

$str = (substr($str,-1) == ',') ? substr($str, 0, -1) : $str;

or

$str = (substr($str,-1) == ',') ? substr_replace($str, '', -1) : $str;

or, to remove all trailing commas

$str = rtrim($str, ',');
//this removes all of the trailing commas eg 1,2,3,,,, => 1,2,3
//no need of condition check for last comma with rtrim()

or

$str = preg_replace("/,*$/", '', $str);
//RegEx engine overhead

Similarly, to remove first comma (or any other character) from a string you can use this,

$str = ($str[0] == ',') ? substr($str, 1) : $str;

or

$str = ($str[0] == ',') ? substr_replace($str, '',0,1) : $str;

or, to remove all heading commas

$str = ltrim($str, ',');
//this removes all of the trailing commas eg ,,,,,1,2,3 => 1,2,3
//no need of condition check for last comma with ltrim()

or

$str = preg_replace("/^,*/", '', $str);
//RegEx engine overhead

Now the question arises, why to use above methods when ltrim() and rtrim() are already there? The answer is to use methods which are fastest (or at-least faster than others) in our PHP programs.

Related posts:

1. How to create a random string in PHP

To change the default printer to another printer connected to your computer, on Windows XP, follow below steps,

• Click on the Start menu and then click on Printers and Faxes.
  

  how-to-set-default-printer-1

• A window which shows the icons of all the installed printers should appear. Right click on the desired printer icon. A menu should appear.
  

  change-default-printer

• Select (Click) on “Set as Default”.

That’s it! 

To confirm, right click on the printer icon again, a check mark before “Set as Default” should be there.

Even after setting a printer as the default, you can still print from other installed printers. The Print dialog box offers you a selection each time you print.

<?php
$fileURL = "http://www.some-domain.com/image.jpg";
echo "Checking the existence of $fileURL<br>";
?>

Method 1:

<?php
$a = microtime(true);                                    //start time in microseconds of 1st method
echo date("d/m/y : H:i:s", time()), " ",$a, "<br>";
get_http_response_code($fileURL);      //fast but not fool proof
echo "<br>";
$b = microtime(true);                                   //start time in microseconds of 2nd method
echo date("d/m/y : H:i:s", time()), " ", $b, "<br>";
echo "difference = ",$b-$a,"<br>";           //difference between 2nd and 1st
?>

Method 2:

<?php
isPartOfString($fileURL);
echo "<br>";
$c = microtime(true);                                  //start time in microseconds of 3rd method
echo date("d/m/y : H:i:s", time()), " ", $c, "<br>";
echo "difference = ",$c-$b,"<br>";         //difference between 3rd and 2nd
?>

Method 3:

<?php
matchCode($fileURL);
echo "<br>";
$d = microtime(true);
echo date("d/m/y : H:i:s", time()), " ", $d, "<br>";
echo "difference = ",$d-$c,"<br>";
?>

Method 4:

<?php
check_url($fileURL);
echo "<br>";
$e = microtime(true);
echo date("d/m/y : H:i:s", time()), " ", $e, "<br>";
echo "difference = ",$e-$d,"<br>";
?>

Method 5:

<?php
http_file_exists($fileURL);
$f = microtime(true);
echo "difference = ",$f-$e,"
";
?>

<?php
function isPartOfString($fileURL)
{
   $getHeaders = @get_headers($fileURL);
   $str = $getHeaders[0];
   // 200 is the response code in the very first line of the headers when some file is found.
   // 3rd param starts search after HTTP/1
   $pos = strpos($str, ' 200 ', 5);   // Note the space before and after 200

   // Note: The !== operator should be used below.
   // Using != would not work as expected some times, e.g,
   // if the position of second param in the $str is 0 then statement (0 != false) evaluates
  //to false, though it was found....so take care of context also while forming conditions

   if ($pos !== false) {
   // now we can be sure that the func strpos returned something not in boolean context
      //returned pos is irrestive of offset
      if($pos > 5)
      {
         echo "File found";
      }
   }
   else {
      //echo "The string '$findme' was not found in the string '$mystring'";
      echo "File not found";
   }
}
?>

<?php
function matchCode($theURL)
{
   $headers = get_headers($theURL);
   //this function uses regular expression engine, so might be a bit slow
   if (preg_match("/\s200\s/", $headers[0])) {
      echo "File found";
   }
   else  {
      echo "File not found";
     }
}
?>

<?php
function get_http_response_code($theURL) {
   $headers = get_headers($theURL);

   //this works only when position of the response code (200) dosn't alter in future
   if (substr($headers[0], 9, 3) == 200) 
   echo "File found";
   else
   echo "File not found";
}
?>

<?php
function check_url($url) {
   $c = curl_init();
   curl_setopt($c, CURLOPT_URL, $url);
   curl_setopt($c, CURLOPT_HEADER, 1); // get the header
   curl_setopt($c, CURLOPT_NOBODY, 1); // body not required
   curl_setopt($c, CURLOPT_RETURNTRANSFER, 1); // get response as a string from curl_exec, not echo it
   curl_setopt($c, CURLOPT_FRESH_CONNECT, 1); // don't use a cached version of the url
   if (!curl_exec($c)) {
      return false;
   }

   $httpcode = curl_getinfo($c, CURLINFO_HTTP_CODE);
   if($httpcode === 200)   // not <400
   {
       echo "File found $httpcode <br>";
   }
   else
   {
        echo "File not found<br>";
   }
   #return ($httpcode < 400);
}
?>

<?php
function http_file_exists($url)
{
   $f = @fopen($url,"r"); //supress warnings by @
   if($f)
   {
      fclose($f);
      echo "File found ";
      return true;
   }
   echo "File not found ";
   return false;
}
?>

<?php
$s = ""; //random string
$sLength = 35; //random string length (you can put any number, you like your string to be in length)

//allowable chars in the wanted random string (add other chars but avoid chars having special meanings to OS)
$a = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_';
for($i = 0, $z = strlen($a)-1; $i != $sLength; $i++)
{
     $x = rand(0,$z);
     $s .= $a{$x};
}
echo $s;
?>