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run code in 150+ php & hhvm versions
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<?php for ($a = $b = []; count($a) < 4; $b = &$a[], $b = $a) ; var_dump($a);
Output for 5.4.0 - 7.1.0
array(4) { [0]=> &array(1) { [0]=> *RECURSION* } [1]=> &array(2) { [0]=> &array(1) { [0]=> *RECURSION* } [1]=> *RECURSION* } [2]=> &array(3) { [0]=> &array(1) { [0]=> *RECURSION* } [1]=> &array(2) { [0]=> &array(1) { [0]=> *RECURSION* } [1]=> *RECURSION* } [2]=> *RECURSION* } [3]=> &array(4) { [0]=> &array(1) { [0]=> *RECURSION* } [1]=> &array(2) { [0]=> &array(1) { [0]=> *RECURSION* } [1]=> *RECURSION* } [2]=> &array(3) { [0]=> &array(1) { [0]=> *RECURSION* } [1]=> &array(2) { [0]=> &array(1) { [0]=> *RECURSION* } [1]=> *RECURSION* } [2]=> *RECURSION* } [3]=> *RECURSION* } }
Output for 4.4.2 - 4.4.9, 5.1.0 - 5.3.29
Parse error: syntax error, unexpected '[' in /in/J0TpV on line 3
Process exited with code 255.
Output for 4.3.0 - 4.3.1, 4.3.5 - 4.4.1, 5.0.0 - 5.0.5
Parse error: parse error, unexpected '[' in /in/J0TpV on line 3
Process exited with code 255.
Output for 4.3.2 - 4.3.4
Parse error: parse error in /in/J0TpV on line 3
Process exited with code 255.