21 Really Useful & Handy PHP Code Snippets

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　　PHP is the most widely used web based programming language that powers millions of websites including some of the most popular ones like Facebook. Here are 21 really useful and handy PHP code snippets that every type of PHP developer will find useful.

1.Human Readable Random String
This code will create a human readable string that will look more close to dictionary words, useful for captchas.
/**************
*@length - length of random string (must be a multiple of 2)
**************/ 
function readable_random_string($length = 6){ 
    $conso=array("b","c","d","f","g","h","j","k","l", 
    "m","n","p","r","s","t","v","w","x","y","z"); 
    $vocal=array("a","e","i","o","u"); 
    $password=""; 
    srand ((double)microtime()*1000000); 
    $max = $length/2; 
    for($i=1; $i<=$max; $i++) 
    { 
    $password.=$conso[rand(0,19)]; 
    $password.=$vocal[rand(0,4)]; 
    } 
    return $password; 
} 
/**************
*@length - length of random string (must be a multiple of 2)
**************/
function readable_random_string($length = 6){
    $conso=array("b","c","d","f","g","h","j","k","l",
    "m","n","p","r","s","t","v","w","x","y","z");
    $vocal=array("a","e","i","o","u");
    $password="";
    srand ((double)microtime()*1000000);
    $max = $length/2;
    for($i=1; $i<=$max; $i++)
    {
    $password.=$conso[rand(0,19)];
    $password.=$vocal[rand(0,4)];
    }
    return $password;
}

2.Generate a Random String
If you don’t need human readable string, then use this function instead, which will create a random string you can use for user id’s etc.
/*************
*@l - length of random string
*/ 
function generate_rand($l){ 
  $c= "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"; 
  srand((double)microtime()*1000000); 
  for($i=0; $i<$l; $i++){ 
      $rand.= $c[rand()%strlen($c)]; 
  } 
  return $rand; 
} 
/*************
*@l - length of random string
*/
function generate_rand($l){
  $c= "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
  srand((double)microtime()*1000000);
  for($i=0; $i<$l; $i++) {
      $rand.= $c[rand()%strlen($c)];
  }
  return $rand;
}

3.Encode Email Address
With this snippet, you can encode any email address into HTML entities so that spam bots do not find it.
function encode_email($email='info@domain.com', $linkText='Contact Us', $attrs ='class="emailencoder"' ) 
{ 
    // remplazar aroba y puntos 
    $email = str_replace('@', '&#64;', $email); 
    $email = str_replace('.', '&#46;', $email); 
    $email = str_split($email, 5); 
 
    $linkText = str_replace('@', '&#64;', $linkText); 
    $linkText = str_replace('.', '&#46;', $linkText); 
    $linkText = str_split($linkText, 5); 
 
    $part1 = '<a href="ma'; 
    $part2 = 'ilto&#58;'; 
    $part3 = '" '. $attrs .' >'; 
    $part4 = '</a>'; 
 
    $encoded = '<script type="text/javascript">'; 
    $encoded .= "document.write('$part1');"; 
    $encoded .= "document.write('$part2');"; 
    foreach($email as $e) 
    { 
            $encoded .= "document.write('$e');"; 
    } 
    $encoded .= "document.write('$part3');"; 
    foreach($linkText as $l) 
    { 
            $encoded .= "document.write('$l');"; 
    } 
    $encoded .= "document.write('$part4');"; 
    $encoded .= '</script>'; 
 
    return $encoded; 
} 
function encode_email($email='info@domain.com', $linkText='Contact Us', $attrs ='class="emailencoder"' )
{
    // remplazar aroba y puntos
    $email = str_replace('@', '&#64;', $email);
    $email = str_replace('.', '&#46;', $email);
    $email = str_split($email, 5);

    $linkText = str_replace('@', '&#64;', $linkText);
    $linkText = str_replace('.', '&#46;', $linkText);
    $linkText = str_split($linkText, 5);

    $part1 = '<a href="ma';
    $part2 = 'ilto&#58;';
    $part3 = '" '. $attrs .' >';
    $part4 = '</a>';

    $encoded = '<script type="text/javascript">';
    $encoded .= "document.write('$part1');";
    $encoded .= "document.write('$part2');";
    foreach($email as $e)
    {
            $encoded .= "document.write('$e');";
    }
    $encoded .= "document.write('$part3');";
    foreach($linkText as $l)
    {
            $encoded .= "document.write('$l');";
    }
    $encoded .= "document.write('$part4');";
    $encoded .= '</script>';

    return $encoded;
}

4.Validate email Address
E-mail validation is perhaps the most used validation in web forms, this code will validate email address and also optionally check the MX records of the domain provided in email address to make email validation more robust.
function is_valid_email($email, $test_mx = false) 
{ 
    if(eregi("^([_a-z0-9-]+)(\.[_a-z0-9-]+)*@([a-z0-9-]+)(\.[a-z0-9-]+)*(\.[a-z]{2,4})$", $email)) 
        if($test_mx) 
        { 
            list($username, $domain) = split("@", $email); 
            return getmxrr($domain, $mxrecords); 
        } 
        else 
            return true; 
    else 
        return false; 
} 
function is_valid_email($email, $test_mx = false)
{
    if(eregi("^([_a-z0-9-]+)(\.[_a-z0-9-]+)*@([a-z0-9-]+)(\.[a-z0-9-]+)*(\.[a-z]{2,4})$", $email))
        if($test_mx)
        {
            list($username, $domain) = split("@", $email);
            return getmxrr($domain, $mxrecords);
        }
        else
            return true;
    else
        return false;
}

5. List Directory Contents
function list_files($dir) 
{ 
    if(is_dir($dir)) 
    { 
        if($handle = opendir($dir)) 
        { 
            while(($file = readdir($handle)) !== false) 
            { 
                if($file != "." && $file != ".." && $file != "Thumbs.db") 
                { 
                    echo '<a target="_blank" href="'.$dir.$file.'">'.$file.'</a><br>'."\n"; 
                } 
            } 
            closedir($handle); 
        } 
    } 
} 
function list_files($dir)
{
    if(is_dir($dir))
      {
          if($handle = opendir($dir))
          {
              while(($file = readdir($handle)) !== false)
              {
                  if($file != "." && $file != ".." && $file != "Thumbs.db")
                  {
                      echo '<a target="_blank" href="'.$dir.$file.'">'.$file.'</a><br>'."\n";
                  }
              }
              closedir($handle);
          }
    }
}

6. Destroy Directory
Delete a directory including its contents.
/*****
*@dir - Directory to destroy
*@virtual[optional]- whether a virtual directory
*/ 
function destroyDir($dir, $virtual = false) 
{ 
    $ds = DIRECTORY_SEPARATOR; 
    $dir = $virtual ? realpath($dir) : $dir; 
    $dir = substr($dir, -1) == $ds ? substr($dir, 0, -1) : $dir; 
    if (is_dir($dir) && $handle = opendir($dir)) 
    { 
        while ($file = readdir($handle)) 
        { 
            if ($file == '.' || $file == '..') 
            { 
                continue; 
            } 
            elseif (is_dir($dir.$ds.$file)) 
            { 
                destroyDir($dir.$ds.$file); 
            } 
            else 
            { 
                unlink($dir.$ds.$file); 
            } 
        } 
        closedir($handle); 
        rmdir($dir); 
        return true; 
    } 
    else 
    { 
        return false; 
    } 
} 
/*****
*@dir - Directory to destroy
*@virtual[optional]- whether a virtual directory
*/
function destroyDir($dir, $virtual = false)
{
    $ds = DIRECTORY_SEPARATOR;
    $dir = $virtual ? realpath($dir) : $dir;
    $dir = substr($dir, -1) == $ds ? substr($dir, 0, -1) : $dir;
    if (is_dir($dir) && $handle = opendir($dir))
    {
        while ($file = readdir($handle))
        {
            if ($file == '.' || $file == '..')
            {
                continue;
            }
            elseif (is_dir($dir.$ds.$file))
            {
                destroyDir($dir.$ds.$file);
            }
            else
            {
                unlink($dir.$ds.$file);
            }
        }
        closedir($handle);
        rmdir($dir);
        return true;
    }
    else
    {
        return false;
    }
}

7.Parse JSON Data
With most of the popular web services like Twitter providing their data through APIs, it is always helpful to know how to parse API data which is sent in various formats including JSON, XML etc.
$json_string='{"id":1,"name":"foo","email":"foo@foobar.com","interest":["wordpress","php"]} '; 
$obj=json_decode($json_string); 
echo $obj->name; //prints foo 
echo $obj->interest[1]; //prints php 
$json_string='{"id":1,"name":"foo","email":"foo@foobar.com","interest":["wordpress","php"]} ';
$obj=json_decode($json_string);
echo $obj->name; //prints foo
echo $obj->interest[1]; //prints php

8.Parse XML Data
//xml string 
$xml_string="<?xml version='1.0'?>
<users>
   <user id='398'>
      <name>Foo</name>
      <email>foo@bar.com</name>
   </user>
   <user id='867'>
      <name>Foobar</name>
      <email>foobar@foo.com</name>
   </user>
</users>"; 
 
//load the xml string using simplexml 
$xml = simplexml_load_string($xml_string); 
 
//loop through the each node of user 
foreach ($xml->user as $user) 
{ 
   //access attribute 
   echo $user['id'], '  '; 
   //subnodes are accessed by -> operator 
   echo $user->name, '  '; 
   echo $user->email, '<br />'; 
} 

//xml string
$xml_string="<?xml version='1.0'?>
<users>
   <user id='398'>
      <name>Foo</name>
      <email>foo@bar.com</name>
   </user>
   <user id='867'>
      <name>Foobar</name>
      <email>foobar@foo.com</name>
   </user>
</users>";

//load the xml string using simplexml
$xml = simplexml_load_string($xml_string);

//loop through the each node of user
foreach ($xml->user as $user)
{
   //access attribute
   echo $user['id'], '  ';
   //subnodes are accessed by -> operator
   echo $user->name, '  ';
   echo $user->email, '<br />';
}

9.Create Post Slugs
Create user friendly post slugs from title string to use within URLs.
function create_slug($string){ 
    $slug=preg_replace('/[^A-Za-z0-9-]+/', '-', $string); 
    return $slug; 
} 
function create_slug($string){
    $slug=preg_replace('/[^A-Za-z0-9-]+/', '-', $string);
    return $slug;
}

10.Get Real IP Address of Client
This function will fetch the real IP address of the user even if he is behind a proxy server.
function getRealIpAddr() 
{ 
    if (!emptyempty($_SERVER['HTTP_CLIENT_IP'])) 
    { 
        $ip=$_SERVER['HTTP_CLIENT_IP']; 
    } 
    elseif (!emptyempty($_SERVER['HTTP_X_FORWARDED_FOR'])) 
    //to check ip is pass from proxy 
    { 
        $ip=$_SERVER['HTTP_X_FORWARDED_FOR']; 
    } 
    else 
    { 
        $ip=$_SERVER['REMOTE_ADDR']; 
    } 
    return $ip; 
} 
function getRealIpAddr()
{
    if (!empty($_SERVER['HTTP_CLIENT_IP']))
    {
        $ip=$_SERVER['HTTP_CLIENT_IP'];
    }
    elseif (!empty($_SERVER['HTTP_X_FORWARDED_FOR']))
    //to check ip is pass from proxy
    {
        $ip=$_SERVER['HTTP_X_FORWARDED_FOR'];
    }
    else
    {
        $ip=$_SERVER['REMOTE_ADDR'];
    }
    return $ip;
}

11.Force file Download
Provide files to the user by forcing them to download.
/********************
*@file - path to file
*/ 
function force_download($file) 
{ 
    if ((isset($file))&&(file_exists($file))) { 
       header("Content-length: ".filesize($file)); 
       header('Content-Type: application/octet-stream'); 
       header('Content-Disposition: attachment; filename="' . $file . '"'); 
       readfile("$file"); 
    } else { 
       echo "No file selected"; 
    } 
} 
/********************
*@file - path to file
*/
function force_download($file)
{
    if ((isset($file))&&(file_exists($file))) {
       header("Content-length: ".filesize($file));
       header('Content-Type: application/octet-stream');
       header('Content-Disposition: attachment; filename="' . $file . '"');
       readfile("$file");
    } else {
       echo "No file selected";
    }
}

12.Creating a Tag Cloud
function getCloud( $data = array(), $minFontSize = 12, $maxFontSize = 30 ) 
{ 
    $minimumCount = min($data); 
    $maximumCount = max($data); 
    $spread       = $maximumCount - $minimumCount; 
    $cloudHTML    = ''; 
    $cloudTags    = array(); 
 
    $spread == 0 && $spread = 1; 
 
    foreach( $data as $tag => $count ) 
    { 
        $size = $minFontSize + ( $count - $minimumCount ) 
            * ( $maxFontSize - $minFontSize ) / $spread; 
        $cloudTags[] = '<a style="font-size: ' . floor( $size ) . 'px' 
        . '" class="tag_cloud" href="#" title="\'' . $tag  . 
        '\' returned a count of ' . $count . '">' 
        . htmlspecialchars( stripslashes( $tag ) ) . '</a>'; 
    } 
 
    return join( "\n", $cloudTags ) . "\n"; 
} 
/**************************
****   Sample usage    ***/ 
$arr = Array('Actionscript' => 35, 'Adobe' => 22, 'Array' => 44, 'Background' => 43, 
    'Blur' => 18, 'Canvas' => 33, 'Class' => 15, 'Color Palette' => 11, 'Crop' => 42, 
    'Delimiter' => 13, 'Depth' => 34, 'Design' => 8, 'Encode' => 12, 'Encryption' => 30, 
    'Extract' => 28, 'Filters' => 42); 
echo getCloud($arr, 12, 36); 

function getCloud( $data = array(), $minFontSize = 12, $maxFontSize = 30 )
{
    $minimumCount = min($data);
    $maximumCount = max($data);
    $spread       = $maximumCount - $minimumCount;
    $cloudHTML    = '';
    $cloudTags    = array();

    $spread == 0 && $spread = 1;

    foreach( $data as $tag => $count )
    {
        $size = $minFontSize + ( $count - $minimumCount )
            * ( $maxFontSize - $minFontSize ) / $spread;
        $cloudTags[] = '<a style="font-size: ' . floor( $size ) . 'px'
        . '" class="tag_cloud" href="#" title="\'' . $tag  .
        '\' returned a count of ' . $count . '">'
        . htmlspecialchars( stripslashes( $tag ) ) . '</a>';
    }

    return join( "\n", $cloudTags ) . "\n";
}
/**************************
****   Sample usage    ***/
$arr = Array('Actionscript' => 35, 'Adobe' => 22, 'Array' => 44, 'Background' => 43,
    'Blur' => 18, 'Canvas' => 33, 'Class' => 15, 'Color Palette' => 11, 'Crop' => 42,
    'Delimiter' => 13, 'Depth' => 34, 'Design' => 8, 'Encode' => 12, 'Encryption' => 30,
    'Extract' => 28, 'Filters' => 42);
echo getCloud($arr, 12, 36);

13.Find Similarity Between Two Strings
PHP includes a function similar_text very rarely used but quite useful that compares two strings and returns the percentage of similarity between two.
similar_text($string1, $string2, $percent); 
//$percent will have the percentage of similarity 

similar_text($string1, $string2, $percent);
//$percent will have the percentage of similarity

14. Use Gravatars in Your Application
With ever increasing popularity of WordPress, Gravatars have become quite popular. It is very easy to integrate them into your application as they provide a very easy to use API.
/******************
*@email - Email address to show gravatar for
*@size - size of gravatar
*@default - URL of default gravatar to use
*@rating - rating of Gravatar(G, PG, R, X)
*/ 
function show_gravatar($email, $size, $default, $rating) 
{ 
    echo '<img src="http://www.gravatar.com/avatar.php?gravatar_id='.md5($email). 
        '&default='.$default.'&size='.$size.'&rating='.$rating.'" width="'.$size.'px"
        height="'.$size.'px" />'; 
} 
/******************
*@email - Email address to show gravatar for
*@size - size of gravatar
*@default - URL of default gravatar to use
*@rating - rating of Gravatar(G, PG, R, X)
*/
function show_gravatar($email, $size, $default, $rating)
{
    echo '<img src="http://www.gravatar.com/avatar.php?gravatar_id='.md5($email).
        '&default='.$default.'&size='.$size.'&rating='.$rating.'" width="'.$size.'px"
        height="'.$size.'px" />';
}

15. Truncate Text at Word Break
This function will truncate strings only at word breaks which can be used to show a teaser for complete article without breaking words.
// Original PHP code by Chirp Internet: www.chirp.com.au 
// Please acknowledge use of this code by including this header. 
function myTruncate($string, $limit, $break=".", $pad="...") { 
    // return with no change if string is shorter than $limit 
    if(strlen($string) <= $limit) 
        return $string;  
 
    // is $break present between $limit and the end of the string? 
    if(false !== ($breakpoint = strpos($string, $break, $limit))) { 
        if($breakpoint < strlen($string) - 1) { 
            $string = substr($string, 0, $breakpoint) . $pad; 
        } 
    } 
    return $string; 
} 
/***** Example ****/ 
$short_string=myTruncate($long_string, 100, ' '); 

// Original PHP code by Chirp Internet: www.chirp.com.au
// Please acknowledge use of this code by including this header.
function myTruncate($string, $limit, $break=".", $pad="...") {
    // return with no change if string is shorter than $limit
    if(strlen($string) <= $limit)
        return $string;

    // is $break present between $limit and the end of the string?
    if(false !== ($breakpoint = strpos($string, $break, $limit))) {
        if($breakpoint < strlen($string) - 1) {
            $string = substr($string, 0, $breakpoint) . $pad;
        }
    }
    return $string;
}
/***** Example ****/
$short_string=myTruncate($long_string, 100, ' ');

16. Zip Files on the Fly
/* creates a compressed zip file */ 
function create_zip($files = array(),$destination = '',$overwrite = false) { 
    //if the zip file already exists and overwrite is false, return false 
    if(file_exists($destination) && !$overwrite) { return false; } 
    //vars 
    $valid_files = array(); 
    //if files were passed in... 
    if(is_array($files)) { 
        //cycle through each file 
        foreach($files as $file) { 
            //make sure the file exists 
            if(file_exists($file)) { 
                $valid_files[] = $file; 
            } 
        } 
    } 
    //if we have good files... 
    if(count($valid_files)) { 
        //create the archive 
        $zip = new ZipArchive(); 
        if($zip->open($destination,$overwrite ? ZIPARCHIVE::OVERWRITE : ZIPARCHIVE::CREATE) !== true) { 
            return false; 
        } 
        //add the files 
        foreach($valid_files as $file) { 
            $zip->addFile($file,$file); 
        } 
        //debug 
        //echo 'The zip archive contains ',$zip->numFiles,' files with a status of ',$zip->status; 
 
        //close the zip -- done! 
        $zip->close(); 
 
        //check to make sure the file exists 
        return file_exists($destination); 
    } 
    else 
    { 
        return false; 
    } 
} 
/***** Example Usage ***/ 
$files=array('file1.jpg', 'file2.jpg', 'file3.gif'); 
create_zip($files, 'myzipfile.zip', true); 

/* creates a compressed zip file */
function create_zip($files = array(),$destination = '',$overwrite = false) {
    //if the zip file already exists and overwrite is false, return false
    if(file_exists($destination) && !$overwrite) { return false; }
    //vars
    $valid_files = array();
    //if files were passed in...
    if(is_array($files)) {
        //cycle through each file
        foreach($files as $file) {
            //make sure the file exists
            if(file_exists($file)) {
                $valid_files[] = $file;
            }
        }
    }
    //if we have good files...
    if(count($valid_files)) {
        //create the archive
        $zip = new ZipArchive();
        if($zip->open($destination,$overwrite ? ZIPARCHIVE::OVERWRITE : ZIPARCHIVE::CREATE) !== true) {
            return false;
        }
        //add the files
        foreach($valid_files as $file) {
            $zip->addFile($file,$file);
        }
        //debug
        //echo 'The zip archive contains ',$zip->numFiles,' files with a status of ',$zip->status;

        //close the zip -- done!
        $zip->close();

        //check to make sure the file exists
        return file_exists($destination);
    }
    else
    {
        return false;
    }
}
/***** Example Usage ***/
$files=array('file1.jpg', 'file2.jpg', 'file3.gif');
create_zip($files, 'myzipfile.zip', true);

17.Unzip Zip File
/**********************
*@file - path to zip file
*@destination - destination directory for unzipped files
*/ 
function unzip_file($file, $destination){ 
    // create object 
    $zip = new ZipArchive() ; 
    // open archive 
    if ($zip->open($file) !== TRUE) { 
        die (’Could not open archive’); 
    } 
    // extract contents to destination directory 
    $zip->extractTo($destination); 
    // close archive 
    $zip->close(); 
    echo 'Archive extracted to directory'; 
} 
/**********************
*@file - path to zip file
*@destination - destination directory for unzipped files
*/
function unzip_file($file, $destination){
    // create object
    $zip = new ZipArchive() ;
    // open archive
    if ($zip->open($file) !== TRUE) {
        die (’Could not open archive’);
    }
    // extract contents to destination directory
    $zip->extractTo($destination);
    // close archive
    $zip->close();
    echo 'Archive extracted to directory';
}

18. Prepend http to a URL
Some times you need to accept some url as input but users seldom add http:// to it, this code will add http:// to the URL if it’s not there.

if (!preg_match("/^(http|ftp):/", $_POST['url'])) { 
   $_POST['url'] = 'http://'.$_POST['url']; 
} 
if (!preg_match("/^(http|ftp):/", $_POST['url'])) {
   $_POST['url'] = 'http://'.$_POST['url'];
}

19.Convert URLs within String into hyperlinks
This function converts URLs and e-mail addresses within a string into clickable hyperlinks.
function makeClickableLinks($text) { 
 $text = eregi_replace('(((f|ht){1}tp://)[-a-zA-Z0-9@:%_+.~#?&//=]+)', 
 '<a href="\1">\1</a>', $text); 
 $text = eregi_replace('([[:space:]()[{}])(www.[-a-zA-Z0-9@:%_+.~#?&//=]+)', 
 '\1<a href="http://\2">\2</a>', $text); 
 $text = eregi_replace('([_.0-9a-z-]+@([0-9a-z][0-9a-z-]+.)+[a-z]{2,3})', 
 '<a href="mailto:\1">\1</a>', $text); 
 
return $text; 
} 

function makeClickableLinks($text) {
 $text = eregi_replace('(((f|ht){1}tp://)[-a-zA-Z0-9@:%_+.~#?&//=]+)',
 '<a href="\1">\1</a>', $text);
 $text = eregi_replace('([[:space:]()[{}])(www.[-a-zA-Z0-9@:%_+.~#?&//=]+)',
 '\1<a href="http://\2">\2</a>', $text);
 $text = eregi_replace('([_.0-9a-z-]+@([0-9a-z][0-9a-z-]+.)+[a-z]{2,3})',
 '<a href="mailto:\1">\1</a>', $text);
return $text;
}

20.Resize Images on the fly
Creating thumbnails of the images is required many a times, this code will be useful to know about the logic of thumbnail generation.
/**********************
*@filename - path to the image
*@tmpname - temporary path to thumbnail
*@xmax - max width
*@ymax - max height
*/ 
function resize_image($filename, $tmpname, $xmax, $ymax) 
{ 
    $ext = explode(".", $filename); 
    $ext = $ext[count($ext)-1]; 
 
    if($ext == "jpg" || $ext == "jpeg") 
        $im = imagecreatefromjpeg($tmpname); 
    elseif($ext == "png") 
        $im = imagecreatefrompng($tmpname); 
    elseif($ext == "gif") 
        $im = imagecreatefromgif($tmpname); 
 
    $x = imagesx($im); 
    $y = imagesy($im); 
 
    if($x <= $xmax && $y <= $ymax) 
        return $im; 
 
    if($x >= $y) { 
        $newx = $xmax; 
        $newy = $newx * $y / $x; 
    } 
    else { 
        $newy = $ymax; 
        $newx = $x / $y * $newy; 
    } 
 
    $im2 = imagecreatetruecolor($newx, $newy); 
    imagecopyresized($im2, $im, 0, 0, 0, 0, floor($newx), floor($newy), $x, $y); 
    return $im2; 
} 
/**********************
*@filename - path to the image
*@tmpname - temporary path to thumbnail
*@xmax - max width
*@ymax - max height
*/
function resize_image($filename, $tmpname, $xmax, $ymax)
{
    $ext = explode(".", $filename);
    $ext = $ext[count($ext)-1];

    if($ext == "jpg" || $ext == "jpeg")
        $im = imagecreatefromjpeg($tmpname);
    elseif($ext == "png")
        $im = imagecreatefrompng($tmpname);
    elseif($ext == "gif")
        $im = imagecreatefromgif($tmpname);

    $x = imagesx($im);
    $y = imagesy($im);

    if($x <= $xmax && $y <= $ymax)
        return $im;

    if($x >= $y) {
        $newx = $xmax;
        $newy = $newx * $y / $x;
    }
    else {
        $newy = $ymax;
        $newx = $x / $y * $newy;
    }

    $im2 = imagecreatetruecolor($newx, $newy);
    imagecopyresized($im2, $im, 0, 0, 0, 0, floor($newx), floor($newy), $x, $y);
    return $im2;
}

21.Detect AJAX Request
Most of the JavaScript frameworks like jQuery, mootools send and additional HTTP_X_REQUESTED_WITH header when they make an AJAX request, so that you can detect AJAX request on server side.(source)

if(!emptyempty($_SERVER['HTTP_X_REQUESTED_WITH']) && strtolower($_SERVER['HTTP_X_REQUESTED_WITH']) == 'xmlhttprequest'){ 
    //If AJAX Request Then 
}else{ 
//something else 
} 
if(!empty($_SERVER['HTTP_X_REQUESTED_WITH']) && strtolower($_SERVER['HTTP_X_REQUESTED_WITH']) == 'xmlhttprequest'){
    //If AJAX Request Then
}else{
//something else
}

If you would like to recommend a snippet to include in this list to make this list a more useful resource, tell us about it in comments below.