how to insert a function into a string in php code example

Example 1: php insert character into string

$newstr = substr_replace($oldstr, $str_to_insert, $pos, 0);

Example 2: php append string

<?php
$a = "Hello ";
$b = $a . "World!"; // now $b contains "Hello World!"

$a = "Hello ";
$a .= "World!";     // now $a contains "Hello World!"
?>