The string length of Regular Expression matching in the preg_match function in PHP

The string length of Regular Expression matching in the preg_match function in PHP

This article mainly introduces the string length problem of Regular Expression matching in the preg_match function in PHP. If you also encounter the problem that the preg_match regular expression is always blank or cannot be extracted, this problem may occur. For more information, see

In the project, use the preg_match regular expression to extract the target content. If there is a problem with live or dead, the code will be tested dead.

Later, I suspect that PHP's preg_match has a string length limit, and found that the value of "pcre. backtrack_limit" is set to only 100000 by default.

Solution: ini_set ('pcre. backtrack_limit ', 999999999 );

Note: this parameter is available after php 5.2.0.

For more information, see pcre. recursion_limit.

Pcre. recursion_limit is the recursive limitation of PCRE. If this item is set to a large value, it will consume the available stacks of all processes and eventually cause PHP to crash.

You can also modify the configuration to restrict: ini_set ('pcre. recursion_limit ', 99999 );

In actual project applications, it is best to set the memory limit: ini_set ('memory _ limit ', '64m');, which makes it safer.