Online PHP editor | output for U6arm

<?php class Out extends Exception { private $value; function __construct($value) { $this->value = $value; } function getValue() { return $this->value; } } function out($value = NULL) { throw new Out($value); } function mul($x, $y) { try { return ($x ?? out('x is NULL')) * ($y ?? out('y is NULL')); } catch (Out $out) { return $out->getValue(); } } var_export(mul(3, 4)); print "\n"; var_export(mul(3, NULL)); print "\n"; var_export(mul(NULL, 4)); print "\n";