Automatic Conversion to array is not possible in PHP. Why?

The behavior of an automatic conversion to array is currently undefined in PHP. Because PHP supports indexing into strings via offsets using the same syntax as array indexing.

E.g.,

<?php
 
$a    = 'car'; // $a is a string
$a[0] = 'b';   // $a is still a string
echo $a;       // bar 

?>