count_chars
(PHP 4, PHP 5)
count_chars — Return information about characters used in a string
Description
Counts the number of occurrences of every bytevalue (0..255) in
string
and returns it in various ways.
Parameters

string

The examined string.

mode

See return values.
Return Values
Depending on mode
count_chars() returns one of the following:
 0  an array with the bytevalue as key and the frequency of every byte as value.
 1  same as 0 but only bytevalues with a frequency greater than zero are listed.
 2  same as 0 but only bytevalues with a frequency equal to zero are listed.
 3  a string containing all unique characters is returned.
 4  a string containing all not used characters is returned.
Examples
Example #1 count_chars() example
<?php
$data = "Two Ts and one F.";
foreach (count_chars($data, 1) as $i => $val) {
echo "There were $val instance(s) of \"" , chr($i) , "\" in the string.\n";
}
?>
The above example will output:
There were 4 instance(s) of " " in the string. There were 1 instance(s) of "." in the string. There were 1 instance(s) of "F" in the string. There were 2 instance(s) of "T" in the string. There were 1 instance(s) of "a" in the string. There were 1 instance(s) of "d" in the string. There were 1 instance(s) of "e" in the string. There were 2 instance(s) of "n" in the string. There were 2 instance(s) of "o" in the string. There were 1 instance(s) of "s" in the string. There were 1 instance(s) of "w" in the string.
See Also
 strpos()  Find the position of the first occurrence of a substring in a string
 substr_count()  Count the number of substring occurrences