(PHP 5 >= 5.2.0, PHP 7) Returns the error code of the last PCRE regex execution

(PHP 4, PHP 5) Make regular expression for case insensitive match

(PHP 4, PHP 5, PHP 7) Find the first occurrence of a string

(PHP 4, PHP 5, PHP 7) Perform a regular expression match

(PHP 4, PHP 5, PHP 7) Find the position of the last occurrence of a substring in a string

(PHP 4, PHP 5, PHP 7) Binary safe case-insensitive string comparison

(PHP 5 >= 5.3.0, PHP 7) Convert a 8 bit string to a quoted-printable string

(PECL ssdeep >= 1.0.0) Create a fuzzy hash from a string

(PHP 7) Perform a regular expression search and replace using callbacks

(PHP 4, PHP 5) Case insensitive regular expression match