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<?php function add($x) { return function($y = null) use ($x) { if (is_null($y)) return $x; else return add($x + $y); }; } var_dump(add(2)->__invoke(40)); echo add(2)->__invoke(40)->__invoke();
Output for 5.3.0 - 5.3.29, 5.4.0 - 5.4.45, 5.5.0 - 5.5.38, 5.6.0 - 5.6.40, 7.0.0 - 7.0.33, 7.1.0 - 7.1.33, 7.2.0 - 7.2.33, 7.3.0 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.27, 8.2.0 - 8.2.17, 8.3.0 - 8.3.4
object(Closure)#2 (2) { ["static"]=> array(1) { ["x"]=> int(42) } ["parameter"]=> array(1) { ["$y"]=> string(10) "<optional>" } } 42
Output for 4.4.2 - 4.4.9, 5.1.0 - 5.1.6, 5.2.0 - 5.2.17
Parse error: syntax error, unexpected T_FUNCTION in /in/3YJkN on line 4
Process exited with code 255.
Output for 4.3.0 - 4.3.1, 4.3.5 - 4.3.11, 4.4.0 - 4.4.1, 5.0.0 - 5.0.5
Parse error: parse error, unexpected T_FUNCTION in /in/3YJkN on line 4
Process exited with code 255.
Output for 4.3.2 - 4.3.4
Parse error: parse error in /in/3YJkN on line 4
Process exited with code 255.

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