find and replace in php

str_replace ($search, $replace, $subject);

<?php

echo str_replace("world","Peter","Hello world!");

?> 

echo str_replace("worss","world","Hello worss in PHP!!");

$vowels = array("a", "e", "i", "o", "u", "A", "E", "I", "O", "U");
$onlyconsonants = str_replace($vowels, "", "Hello World of PHP");
// Fornece: Hll Wrld f PHP