The string length problem of regular matching by preg_match function in PHP_PHP tutorial

The string length problem of regular matching by preg_match function in PHP

This article mainly introduces the string length problem of regular matching by preg_match function in PHP. If you also encounter preg_match If the regular content is always blank or cannot be extracted, then you may have encountered this problem. Friends who need it can refer to it

In the project, preg_match is used to extract the target content. There are problems, 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: ini_set('pcre.backtrack_limit', 999999999);

Note: This parameter is available after PHP 5.2.0 version.

In addition, let’s talk about: pcre.recursion_limit

pcre.recursion_limit is the recursion limit of PCRE. If this item is set to a large value, the available stacks of all processes will be consumed, and eventually PHP will crash.

You can also limit it by modifying the configuration: ini_set('pcre.recursion_limit', 99999);

In actual project applications, it is best to limit the memory: ini_set('memory_limit', '64M'); , which is more secure.