smileys for chat script using php

<?php function parseString($message ) {
    $my_smilies = array(
        ':)' => '<img src="images/smiley.gif" alt="" />',
    ':(' => '<img src="images/sad.gif" alt="" />',
   
    );

    return str_replace( array_keys($my_smilies), array_values($my_smilies), $message);
}

echo parseString($message);
?>