string count_chars(string $str [, int $mode])

(PHP 4, PHP 5)

Possible Values for $mode

• 0 = return an array with the ASCII value as the key, and frequency as the value (DEFAULT VALUE)
• 1 = return an array with the ASCII value as the key, and frequency as the value (omit entries where the frequency is zero)
• 2 = return an array with the ASCII value as the key, and frequency as the value
• 3 = return a string that contains all unique characters that were found in the source string ($str)
• 4 = return a string that contains all unique characters that were NOT FOUND in the source string ($str)

Search the source string and compile statistics based on what characters were found in the string and (optionally), which were not. Unless you need to do some statistic analysis on frequency of characters found in a source string, this function will not be of much use to you.

echo count_chars($input, 3);