regex - PHP ereg vs. preg

Question

I have noticed in the PHP regex library there is a choice between ereg and preg. What is the difference? Is one faster than the other and if so, why isn't the slower one deprecated?

Are there any situations where it is better to use one over the other?

Answer 1

Visiting php.net/ereg displays the following:

Warning

This function has been DEPRECATED as of PHP 5.3.0 and REMOVED as of PHP 6.0.0. Relying on this feature is highly discouraged.

Down the page just a bit further and we read this:

Note: preg_match(), which uses a Perl-compatible regular expression syntax, is often a faster alternative to ereg().

Note my emphasis.