This function discards the contents of the output buffer and turns off output buffering.

This modifier turns on additional functionality of PCRE that is incompatible with Perl. Pattern strings are treated as UTF 8. This modifier is available from PHP 4.1.0 or greater on Unix and from PHP 4.2.3 on win32.

This modifier turns on additional functionality of PCRE that is incompatible with Perl. Any backslash in a pattern that is followed by a letter that has no special meaning causes an error, thus reserving these combinations for future expansion. By default, as in Perl, a backslash followed by a letter with no special meaning is treated as a literal. There are at present no other features controlled by this modifier.