pcre.backtrack_limit defaults to 100k. This is rather conservative.
It is limited by RAM size, not the ulimit on stack-size.
On a (2009-era) netbook, I can set pcre.backtrack_limit to 100 million, and the regex will happily process a 90 million character string in about 3 seconds. YMMV.
Runtime Configuration
The behaviour of these functions is affected by settings in php.ini.
| Name | Default | Changeable | Changelog |
|---|---|---|---|
| pcre.backtrack_limit | "1000000" | PHP_INI_ALL | Available since PHP 5.2.0. |
| pcre.recursion_limit | "100000" | PHP_INI_ALL | Available since PHP 5.2.0. |
| pcre.jit | "1" | PHP_INI_ALL | Available since PHP 7.0.0. |
Here's a short explanation of the configuration directives.
-
pcre.backtrack_limitinteger -
PCRE's backtracking limit. Defaults to 100000 for PHP < 5.3.7.
-
pcre.recursion_limitinteger -
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).
-
pcre.jitboolean -
Whether PCRE's just-in-time compilation is going to be used.
add a note
User Contributed Notes 2 notes
php at richardneill dot org ¶
4 years ago
chris at ocproducts dot com ¶
5 years ago
pcre.backtrack_limit sets the maximum bind length PREG calls (e.g. preg_replace_callback) can make. However the actual maximum seems to be approximately half the value set here, possibly due to the character encoding that PCRE runs with internally.
