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* } } }
?>
It is true recursion, and *RECURSION* is not a real error message.
It's not problematic, because $test is not actively recurring, and in this case var_dump is smart enough to stop before exhausting memory.
I would guess that detecting such a loop is non-trivial, and would be immediately apparent at runtime if the behaviour was incorrect.
Why is it problematic? PHP is smart enough to identify that an array is being recursively called.
The same happens if you print_r($GLOBALS), I see no harm in this.
You're setting a reference, that is, a pointer so there is no true recursion, no loop. So no, it shouldn't throw an error.
Actualy the *RECURSION* message is a error message, which ends the script execution.
Else it would execute it till the memory limit is reaced.
$testin the same expression that defined$test.$test = array('test'); $test[]=&$test;is pretty clear. But yours …$x =& $y; $y = 5;for example is valid, with$yhaving never been defined earlier.