(PHP 4 >= 4.4.3, PHP 5 >= 5.1.3, PHP 7) Check if the string is valid for the specified encoding

(PHP 4 >= 4.0.6, PHP 5, PHP 7) Get part of string

(PHP 4 >= 4.0.6, PHP 5, PHP 7) Find position of first occurrence of string in a string

(PHP 4 >= 4.0.6, PHP 5, PHP 7) Return width of string

(PHP 5 >= 5.2.0, PHP 7) Finds position of first occurrence of a string within another, case insensitive

(PHP 4 >= 4.2.0, PHP 5, PHP 7) Set start point of next regular expression match

(PHP 4 >= 4.2.0, PHP 5, PHP 7) Replace regular expression with multibyte support

(PHP 4 >= 4.3.0, PHP 5, PHP 7) Perform case folding on a string

(PHP 4 >= 4.0.6, PHP 5, PHP 7) Send encoded mail

(PHP 4 >= 4.3.0, PHP 5, PHP 7) Count the number of substring occurrences