(PHP 4, PHP 5, PHP 7) String comparisons using a "natural order" algorithm

(PHP 4, PHP 5, PHP 7) Reverse a string string

(PHP 5, PHP 7) Search a string for any of a set of characters

(PHP 5, PHP 7) Find the position of the first occurrence of a case-insensitive substring in a string

(PHP 4, PHP 5, PHP 7) Join array elements with a string

(PHP 4 >= 4.0.2, PHP 5, PHP 7) Wraps a string to a given number of characters

(PHP 4, PHP 5, PHP 7) Calculate the similarity between two strings

(PHP 4, PHP 5, PHP 7) Set locale information

(PHP 5, PHP 7) Write a formatted string to a stream

(PHP 4, PHP 5, PHP 7) Convert all applicable characters to HTML entities