how to remove characters from a string php code example

Example 1: php remove text from string

<?php
  //Replace the characters "world" in the string "Hello world!" with "Peter":
echo str_replace("world","Peter","Hello world!");
?>

Example 2: str_replace php variable

$var1 = 'hello_john';
$var2 = str_replace("_", "-", $var1);
echo $var2; // hello-john