15个实用的PHP正则表达式

$url = "http://komunitasweb.com/"; 
if (preg_match('/^(http|https|ftp)://([A-Z0-9][A-Z0-9_-]*(?:.[A-Z0-9][A-Z0-9_-]*)+):?(d+)?/?/i', $url)) { 
  echo "Your url is ok."; 
} else { 
  echo "Wrong url."; 
}

$text = "Sample sentence from KomunitasWeb, regex has become popular in web programming. Now we learn regex. According to wikipedia, Regular expressions (abbreviated as regex or 

regexp, with plural forms regexes, regexps, or regexen) are written in a formal language that can be interpreted by a regular expression processor"; 
$text = preg_replace("/b(regex)b/i", '<span style="background:#5fc9f6">1</span>', $text); 
echo $text;

echo $title; 

Now, just before the modified line, add this code: 

<?php 
  $title   = get_the_title(); 
  $keys= explode(" ",$s); 
  $title   = preg_replace('/('.implode('|', $keys) .')/iu', 
    '<strong>\0</strong>', 
    $title); 
?> 

Save the search.php file and open style.css. Append the following line to it: 

strong.search-excerpt { background: yellow; }

$images = array(); 
preg_match_all('/(img|src)=("|')[^"'>]+/i', $data, $media); 
unset($data); 
$data=preg_replace('/(img|src)("|'|="|=')(.*)/i',"$3",$media[0]); 
foreach($data as $url) 
{ 
  $info = pathinfo($url); 
  if (isset($info['extension'])) 
  { 
    if (($info['extension'] == 'jpg') || 
    ($info['extension'] == 'jpeg') || 
    ($info['extension'] == 'gif') || 
    ($info['extension'] == 'png')) 
    array_push($images, $url); 
  } 
}

$text = preg_replace("/s(w+s)1/i", "$1", $text);

$text = preg_replace("/.+/i", ".", $text);

function get_tag( $tag, $xml ) { 
 $tag = preg_quote($tag); 
 preg_match_all('{<'.$tag.'[^>]*>(.*?)</'.$tag.'>.'}', 
          $xml, 
          $matches, 
          PREG_PATTERN_ORDER); 

 return $matches[1]; 
}

function get_tag( $attr, $value, $xml, $tag=null ) { 
 if( is_null($tag) ) 
  $tag = '\w+'; 
 else 
  $tag = preg_quote($tag); 

 $attr = preg_quote($attr); 
 $value = preg_quote($value); 

 $tag_regex = "/<(".$tag.")[^>]*$attr\s*=\s*". 
        "(['\"])$value\\2[^>]*>(.*?)<\/\\1>/" 

 preg_match_all($tag_regex, 
         $xml, 
         $matches, 
         PREG_PATTERN_ORDER); 

 return $matches[3]; 
}

$string = "#555555"; 
if (preg_match('/^#(?:(?:[a-fd]{3}){1,2})$/i', $string)) { 
echo "example 6 successful."; 
}

$fp = fopen("http://www.catswhocode.com/blog","r"); 
while (!feof($fp) ){ 
  $page .= fgets($fp, 4096); 
} 

$titre = eregi("<title>(.*)</title>",$page,$regs); 
echo $regs[1]; 
fclose($fp);

//Logs: Apache web server 
//Successful hits to HTML files only. Useful for counting the number of page views. 
'^((?#client IP or domain name)S+)s+((?#basic authentication)S+s+S+)s+[((?#date and time)[^]]+)]s+"(?:GET|POST|HEAD) ((?#file)/[^ ?"]+?.html?)??((?#parameters)[^ ?"]+)? HTTP/[0-9.]+"s+(?#status code)200s+((?#bytes transferred)[-0-9]+)s+"((?#referrer)[^"]*)"s+"((?#user agent)[^"]*)"$' 

//Logs: Apache web server 
//404 errors only 
'^((?#client IP or domain name)S+)s+((?#basic authentication)S+s+S+)s+[((?#date and time)[^]]+)]s+"(?:GET|POST|HEAD) ((?#file)[^ ?"]+)??((?#parameters)[^ ?"]+)? HTTP/[0-9.]+"s+(?#status code)404s+((?#bytes transferred)[-0-9]+)s+"((?#referrer)[^"]*)"s+"((?#user agent)[^"]*)"$'

preg_replace('B"b([^"x84x93x94rn]+)b"B', '?1?', $text);

'A(?=[-_a-zA-Z0-9]*?[A-Z])(?=[-_a-zA-Z0-9]*?[a-z])(?=[-_a-zA-Z0-9]*?[0-9])[-_a-zA-Z0-9]{6,}z'

<?php if (have_posts()) : ?> 
<?php while (have_posts()) : the_post(); ?> 

<?php 
$szPostContent = $post->post_content; 
$szSearchPattern = '~<img [^>]* />~'; 

// Run preg_match_all to grab all the images and save the results in $aPics 
preg_match_all( $szSearchPattern, $szPostContent, $aPics ); 

// Check to see if we have at least 1 image 
$iNumberOfPics = count($aPics[0]); 

if ( $iNumberOfPics > 0 ) { 
   // Now here you would do whatever you need to do with the images 
   // For this example the images are just displayed 
   for ( $i=0; $i < $iNumberOfPics ; $i++ ) { 
     echo $aPics[0][$i]; 
   }; 
}; 

endwhile; 
endif; 
?> 

$texte='A text with a smiley '; 
echo str_replace(':-)','<img src="smileys/souriant.png">',$texte);

<meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> 
<?php 
  $str = ' 
    <a href="http://www.jobbole.com/">jobbole</a>其他字符 
    <a href="http://www.sohu.com/">sohu</a> 
    <a href="http://www.sohu.com/"><img src="http://www.fashion-press.net/img/news/3176/mot_06.jpg" /></a> 
    <br>'; 

  //echo preg_replace("/(<a.*?>)(<img.*?>)(<\/a>)/", '$2', $str);  
  echo preg_replace("/(<a.*?>)(<img.*?>)(<\/a>)/", '\2', $str);  
?>