Use of PHP preg_match regular expression_PHP tutorial-PHP Tutorial-php.cn

Use of PHP preg_match regular expression_PHP tutorial

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Release： 2016-07-20 11:03:33

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The preg_match() function in PHP is a commonly used function for executing regular expressions. Let me introduce the use of preg_match in detail.

Function usage

int preg_match_all ( string pattern, string subject, array matches [, int flags] )

Example 1

The code is as follows

Copy code

代码如下

复制代码

preg_match_all ("|<[^>]+>(.*)]+>|U","example:

this is a test ",$out, PREG_SET_ORDER);
print $out[0][0].", ".$out[0][1]."n";
print $out[1][0].", ".$out[1][1]."n";
?>

本例将输出：
example: , example:

this is a test , this is a test

preg_match_all ("|<[^>]+>(.*)]+>|U", "example:

this is a test ",$out, PREG_SET_ORDER);
print $out[0][0].", ".$out[0][1]."n";
print $out[1][0].", ".$out[1][1]."n";
?>

This example will output:
example: , example:

代码如下

复制代码

// 从 URL 中取得主机名
preg_match("/^(http://)?([^/]+)/i", "http：//www.***.net/index.html", $matches);
$host = $matches[2];
// 从主机名中取得后面两段
preg_match("/[^./]+.[^./]+$/", $host, $matches);
echo "domain name is: {$matches[0]}n";
?>

本例将输出：

domain name is: PPP．NET

this is a test , this is a test

Example 2

Extract domain name from URL

The code is as follows

Copy code

// Get hostname from URL
preg_match("/^(http://)?([^/]+)/i", "http://www.***.net/index.html", $matches);
$host = $matches[2];
// Get the last two segments from the host name
preg_match("/[^./]+.[^./]+$/", $host, $matches);
echo "domain name is: {$matches[0]}n";
?>

This example will output: domain name is: PPP． NET

代码如下	复制代码
ini_set('pcre.backtrack_limit', 999999999);

preg_match string length problem

The preg_match regular method extracts the target content. There are problems with life and death, and the code is tested to death.

Later I suspected that PHP's preg_match had a string length limit. Sure enough, I found that the value of "pcre.backtrack_limit" was only set to 100000 by default.

Solution:

代码如下	复制代码
ini_set('pcre.recursion_limit', 99999);

Note: This parameter is available after PHP 5.2.0 version.

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