Error but it's working: Notice: Undefined variable: random_row [duplicate]

This question already has an answer here:

• PHP: “Notice: Undefined variable” and “Notice: Undefined index” 14 answers

this is my code:

<?php
$dir = "songs/";
$songs = scandir($dir);
$i = rand(2, sizeof($songs)-1);
?>
<audio src="songs/<?php echo $songs[$i]; ?>" id="audio_player_id" autoplay controls="controls"></audio>

This code get random file from a folder and it's working, but there is an error. The error: Notice: Undefined variable: random_row

How to fix whatever it is and whats the problem?