PHP also supports regular expressions using a Perl_compatible syntax
using the PCRE functions. Those functions
support non_greedy matching, assertions, conditional subpatterns, and a
number of other features not supported by the POSIX_extended regular
These regular expression functions are not binary_safe. The PCRE functions are.
Regular expressions are used for complex string manipulation.
PHP uses the POSIX extended regular expressions as defined by POSIX
1003.2. For a full description of POSIX regular expressions see the regex
man pages included in the regex directory in the PHP distribution. It's
in manpage format, so you'll want to do something along the lines of
man /usr/local/src/regex/regex.7 in order to read it.