count_chars()

count_chars() — Return information about characters used in a string.

count_chars() — Counts the number of occurrences of every byte-value (0..255) in string and returns it in various ways.

Inputs: string: The examined string. mode: See return values.

Returns: Depending on mode count_chars returns one of the following: 0 – an array with the byte-value as key and the frequency of every byte as value. 1 – same as 0 but only byte-values with a frequency greater than zero are listed. 2 – same as 0 but only byte-values with a frequency equal to zero are listed. 3 – a string containing all unique characters is returned. 4 – a string containing all unused characters is returned.