What elements will the following script output?

<?php
$array = array (true => 'a', 1 => 'b');
var_dump ($aray);
?>

• 1 => ‘b’
• True => ‘a’, 1 => ‘b’
• 0 => ‘a’, 1 => ‘b’
• None
• It will output NULL
• I don’t know

Answer:
It will output NULL