Question

Can someone explain what the ‘e’ flag does, or link me to somewhere that does? I couldn’t find anything via google.

Example:

preg_replace("/a(b?)c/e", "search_foo_term('\$1')", $str);

Answer 1

e (PREG_REPLACE_EVAL)

If this modifier
is set, preg_replace() does normal
substitution of backreferences in the
replacement string, evaluates it as
PHP code, and uses the result for
replacing the search string. Single
quotes, double quotes, backslashes ()
and NULL chars will be escaped by
backslashes in substituted
backreferences. Only preg_replace()
uses this modifier; it is ignored by
other PCRE functions.

http://www.php.net/manual/en/reference.pcre.pattern.modifiers.php

So given this example:

preg_replace("/a(b?)c/e", "search_foo_term('\$1')", $str);

The replacement for the entire match will be what search_foo_term() returns when passed the match for b? .