American Standard Code for Information Interchange (ASCII)
ASCII is a character encoding standard used to represent text in computers and electronic devices. It assigns a unique number, or code, to each character, allowing text to be stored and processed digitally.
PHP handles ASCII characters with the functions ord() and chr().
<?php
$string = 'abdc';
echo ord($string[1]); // b = 98
echo chr(100); // d
?>