Write a PHP script to remove comma(s) from the following numeric string

PHP is a server scripting language, and It is a powerful tool for making interactive and dynamic Web-pages. I have used WampServer 2.2 for following example..

<?php
$str = "12,342.78";
$num = str_replace( ',', '', $str);
if( is_numeric($num))
  {
  echo $num."\n";
  }
?>

Result:

12342.78