PHP ID3 "Fatal error" help?

[Knowledge is Key]

when I run my php script to get the id3 of a file:
<?php
$tag = id3_get_tag( "song.mp3" );
print_r($tag);
?>
I get the error:
Fatal error: Call to undefined function id3_get_tag()

 

[cristianods]

Make sure that you have ID3 installed.

Refer to http://php.net/manual/en/book.id3.php for more info.