(PHP 4, PHP 5, PHP 7)
count_chars — Return information about characters used in a string
count_chars ( string $string [, int $mode = 0 ] ) : array|string
 Counts the number of occurrences of every byte-value (0..255) in string and returns it in various ways. 
string
The examined string.
mode
See return values.
 Depending on mode count_chars() returns one of the following: 
| Version | Description | 
|---|---|
| 8.0.0 |  Prior to this version, the function returned false on failure.  |  
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.
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    https://www.php.net/manual/en/function.count-chars.php