Ereg and Preg

[mikilugano]

Hi,
I have a question, which differences are between POSIX Regular Expressions and Perl-Compatible Regular Expressions? Are PCRE specialities RegEx delimiters, pattern modifiers, and assertions?
Thanks.

[laserlight]

According to the PHP manual:

• The PCRE functions "support non-greedy matching, assertions, conditional subpatterns, and a number of other features not supported by the POSIX-extended regular expression syntax" (i.e., ereg).

• The POSIX-extended regular expression functions are not binary-safe, unlike the PCRE functions.

• The PCRE functions are "often a faster alternative to" their POSIX-extended equivalent.

Additionally, in PHP 6, the plan is to move ereg to PECL (i.e., the POSIX-extended regex functions will not be available by default), whereas "the PCRE extension will not be allowed to be disabled".

In short, prefer preg to ereg.