php at richardneill dot org (2011-01-14 09:55:00)

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.

chris at ocproducts dot com (2010-07-02 07:42:48)

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.