PHP Manual

Runtime Configuration

The behaviour of these functions is affected by settings in php.ini.

**PCRE Configuration Options**
Name	Default	Changeable	Changelog
pcre.backtrack_limit	"100000"	PHP_INI_ALL	Available since PHP 5.2.0.
pcre.recursion_limit	"100000"	PHP_INI_ALL	Available since PHP 5.2.0.

For further details and definitions of the PHP_INI_* modes, see the Where a configuration setting may be set.

Here's a short explanation of the configuration directives.

pcre.backtrack_limit integer: PCRE's backtracking limit.
pcre.recursion_limit integer: PCRE's recursion limit. Please note that if you set this value to a high number you may consume all the available process stack and eventually crash PHP (due to reaching the stack size limit imposed by the Operating System).