Detailed explanation of the use of preg_match function in PHP (with code examples)

This article introduces the preg_match() function in PHP in more detail, supplemented by examples, so that everyone can take a look. preg_match() function, how to match regular expression.

Syntax:

preg_match ( string $pattern , string $subject ,array &$matches = ? ,int $flags = 0 ,int $offset = 0 )

• $pattern: Pattern to search, string type.

• $subject: Input string.

• $matches: If the parameter matches is provided, it will be populated as search results. $matches[0] will contain the text matched by the complete pattern, $matches[1] will contain the text matched by the first captured subgroup, and so on.

• $flags: Can be set to a combination of the following tag values: PREG_UNMATCHED_AS_NULL, PREG_OFFSET_CAPTURE

• ##$offset: Optional parameter offset is used to specify Start searching from a certain position in the target string (unit is bytes).

• Return value: number of matches. Its value will be 0 (no match) or 1 because preg_match() will stop matching after the first match. An error occurred preg_match() returned FALSE.

Usage example:

<?php

//从URL中获取主机名称
preg_match(&#39;@^(?:http://)?([^/]+)@i&#39;,
    "http://www.php.cn/index.html", $matches);
$host = $matches[1];

//获取主机名称的后面两部分
preg_match(&#39;/[^.]+\.[^.]+$/&#39;, $host, $matches);
echo "admin name is: {$matches[0]}\n";

?>

输出：admin name is: php.cn

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