change letter in word php code example

Example 1: php str_replace

<?php
//str_replace("Original Value", "Value to be replaced", "String");
$result = str_replace("1", "2", "This is number 1");
// Output: This is number 2
?>

Example 2: php replace every occurrence of character in string

//replaces every occurence of $search with $replace in the string $subject
str_replace ($search, $replace, $subject);