PHP: preg_match

Description

mixed preg_match ( string pattern, string subject [, array &matches [, int flags [, int offset]]] )

Searches subject for a match to the regular expression given in pattern.

If matches is provided, then it is filled with the results of search. $matches[0] will contain the text that matched the full pattern, $matches[1] will have the text that matched the first captured parenthesized subpattern, and so on.

flags can be the following flag:

PREG_OFFSET_CAPTURE: If this flag is passed, for every occurring match the appendant string offset will also be returned. Note that this changes the return value in an array where every element is an array consisting of the matched string at offset 0 and its string offset into subject at offset 1. This flag is available since PHP 4.3.0 .

The flags parameter is available since PHP 4.3.0.

Normally, the search starts from the beginning of the subject string. The optional parameter offset can be used to specify the alternate place from which to start the search. The offset parameter is available since PHP 4.3.3.

Notatka: Using offset is not equivalent to passing substr($subject, $offset) to preg_match() in place of the subject string, because pattern can contain assertions such as ^, $ or (?<=x). Compare:
<?php $subject = "abcdef"; $pattern = '/^def/'; preg_match($pattern, $subject, $matches, PREG_OFFSET_CAPTURE, 3); print_r($matches); ?>
Powyższy przykład wyświetli:
Array
(
)
while this example

<?php $subject = "abcdef"; $pattern = '/^def/'; preg_match($pattern, substr($subject,3), $matches, PREG_OFFSET_CAPTURE); print_r($matches); ?>
will produce
Array
(
    [0] => Array
        (
            [0] => def
            [1] => 0
        )

)

preg_match() returns the number of times pattern matches. That will be either 0 times (no match) or 1 time because preg_match() will stop searching after the first match. preg_match_all() on the contrary will continue until it reaches the end of subject. preg_match() returns FALSE if an error occurred.

Podpowiedź: Do not use preg_match() if you only want to check if one string is contained in another string. Use strpos() or strstr() instead as they will be faster.

Przykład 1. Find the string of text "php"


<?php

// The "i" after the pattern delimiter indicates a case-insensitive search

if (preg_match("/php/i", "PHP is the web scripting language of choice.")) {

    echo "A match was found.";

} else {

    echo "A match was not found.";

}

?>

Przykład 2. Find the word "web"


<?php

/* The \b in the pattern indicates a word boundary, so only the distinct

 * word "web" is matched, and not a word partial like "webbing" or "cobweb" */

if (preg_match("/\bweb\b/i", "PHP is the web scripting language of choice.")) {

    echo "A match was found.";

} else {

    echo "A match was not found.";

}



if (preg_match("/\bweb\b/i", "PHP is the website scripting language of choice.")) {

    echo "A match was found.";

} else {

    echo "A match was not found.";

}

?>

Przykład 3. Getting the domain name out of a URL


<?php

// get host name from URL

preg_match("/^(http:\/\/)?([^\/]+)/i",

    "http://www.php.net/index.html", $matches);

$host = $matches[2];



// get last two segments of host name

preg_match("/[^\.\/]+\.[^\.\/]+$/", $host, $matches);

echo "domain name is: {$matches[0]}\n";

?>

This example will produce:

domain name is: php.net

User Contributed Notes


Here's an improvement on the URL detecting function written by [rickyale at ig dot com dot br]. It detects SRC, HREF and URL links, in addition to URLs in CSS code, and Javascript imports. It also understands html entities(such as &amp;) inside URLs.



<?php

function get_links($url) {

    if( !($body = @file_get_contents($url)) ) return FALSE;

    //Pattern building across multiple lines to avoid page distortion.

    $pattern  = "/((@import\s+[\"'`]([\w:?=@&\/#._;-]+)[\"'`];)|";

    $pattern .= "(:\s*url\s*\([\s\"'`]*([\w:?=@&\/#._;-]+)";

    $pattern .= "([\s\"'`]*\))|<[^>]*\s+(src|href|url)\=[\s\"'`]*";

    $pattern .= "([\w:?=@&\/#._;-]+)[\s\"'`]*[^>]*>))/i";

    //End pattern building.

    preg_match_all ($pattern, $body, $matches);

    return (is_array($matches)) ? $matches:FALSE;

}

?>



$matches[3] will contain Javascript import links, $matches[5] will contain the CSS links, and $matches[8] will contain the regular URL/SRC/HREF HTML links. To get them all in one neat array, you might use something like this:



<?php

function x_array_merge($arr1,$arr2) {

    for($i=0;$i<count($arr1);$i++) {

        $arr[$i]=($arr1[$i] == '')?$arr2[$i]:$arr1[$i];

    }

    return $arr;

}



$url = 'http://www.google.com';

$m = get_links($url);

$links = x_array_merge($m[3],x_array_merge($m[5],$m[8]));

?>


For a system I'm writing, I get MAC addresses in a huge number of formats.  I needed something to handle all of the following:



0-1-2-3-4-5

00:a0:e0:15:55:2f

89 78 77 87 88 9a

0098:8832:aa33

bc de f3-00 e0 90

00e090-ee33cc

::5c:12::3c

0123456789ab



and more.  The function I came up with is:



<?php

function ValidateMAC($str)

{

  preg_match("/^([0-9a-fA-F]{0,2})[-: ]?([0-9a-fA-F]{0,2})[-: ]?([0-9a-fA-F]{0,2})[-: ]?([0-9a-fA-F]{0,2})[-: ]?([0-9a-fA-F]{0,2})[-

: ]?([0-9a-fA-F]{0,2})[-: ]?([0-9a-fA-F]{0,2})$/", $str, $arr);

  if(strlen($arr[0]) != strlen($str))

    return FALSE;

  return sprintf("%02X:%02X:%02X:%02X:%02X:%02X", hexdec($arr[1]), hexdec($arr[2]), hexdec($arr[3]), hexdec($arr[4]), hexdec($arr[5]

), hexdec($arr[6]));

}



   $testStrings = array("0-1-2-3-4-5","00:a0:e0:15:55:2f","89 78 77 87 88 9a","0098:8832:aa33","bc de f3-00 e0 90","00e090-ee33cc","

bf:55:6e:7t:55:44", "::5c:12::3c","0123456789ab");

   foreach($testStrings as $str)

     {

       $res = ValidateMAC($str);

       print("$str => $res<br>");

     }



?>



This returns:



0-1-2-3-4-5 => 00:01:02:03:04:05

00:a0:e0:15:55:2f => 00:A0:E0:15:55:2F

89 78 77 87 88 9a => 89:78:77:87:88:9A

0098:8832:aa33 => 00:98:88:32:AA:33

bc de f3-00 e0 90 => BC:DE:F3:00:E0:90

00e090-ee33cc => 00:E0:90:EE:33:CC

bf:55:6e:7t:55:44 =>

::5c:12::3c => 00:00:5C:12:00:3C

0123456789ab => 01:23:45:67:89:AB