Question

This is the test and the response I get. I think this could be problematic and should throw an error or a notice but I cannot understand why is tolerated.

<?php
    $test = array( 0 => 'test', 1=> &$test );
    var_dump( $test );

    // array(2) { [0]=> string(4) "test" [1]=> &array(2) { [0]=> string(4) "test" [1]=> &array(2) { [0]=> string(4) "test" [1]=> *RECURSION* } } }
?>

Answer 1

It is true recursion, and *RECURSION* is not a real error message.
It’s not problematic, because $test is not actively recurring, and in this case var_dump is smart enough to stop before exhausting memory.