php preg_match will match how many times

php preg_match() function will match once. The preg_match() function is used to search and match strings based on regular expressions, and can return the number of matches; the value of preg_match() will be 0 times (no match) or 1 time, because it will stop after the first match search.

The operating environment of this tutorial: windows7 system, PHP7.1 version, DELL G3 computer

php preg_match() function will match 1 time.

php preg_match() function

The preg_match() function in PHP can search and match strings based on regular expressions. The syntax of the function is as follows:

preg_match($pattern,$subject [, &$matches [, $flags = 0 [, $offset = 0 ]]])

The parameter description is as follows:

• $pattern: the pattern to be searched, which is the edited regular expression;

• $subject: String to search for;

• $matches: Optional parameter (array type), if $matches is provided, it will be populated as the search results. $matches[0] contains the text matched by the complete pattern, $matches[1] contains the text matched by the first capture subgroup, and so on;

• $flags: Yes Optional parameters, $flags can be set to PREG_OFFSET_CAPTURE. If this flag is passed, for each occurrence of a match, the string offset (relative to the target string) will be appended to the return;

• $offset: Optional parameter, used to specify where to start searching in the target string (unit is byte).

preg_match() function can return the number of matches for $pattern, its value will be 0 times (no match) or 1 time, because preg_match() will The search will stop.

Example: Use the preg_match() function to search for a string

<?php
    $subject = "abcdefghijkdef";
    $pattern_1 = &#39;/def/&#39;;
    $num = preg_match($pattern_1, $subject, $matches_1,PREG_OFFSET_CAPTURE,8);
    echo &#39;<pre class="brush:php;toolbar:false">&#39;;
    var_dump($matches_1);
    var_dump($num);   //匹配次数为1次
    $pattern_2 = &#39;/def$/&#39;;
    $num = preg_match($pattern_2, $subject, $matches_2, PREG_OFFSET_CAPTURE, 3);
    var_dump($matches_2);
?>

For the first match, the string will be The 8th bit searches for a substring that matches $pattern_1, and the $matches_2 array contains the matched substring and its position in the target string.

Note that the second regular expression is different from the first regular expression. A positioning symbol $ is added to indicate the position at the end of the matching string.

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