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run code in 300+ PHP versions simultaneously
<?php class A { private $b; public function __construct() { $this->b = new B($this); } } class B { private $a; public function __construct(A $a) { $this->a = $a; } } $a=new A(); var_dump($a); var_export($a); print_r($a);

preferences:
38.58 ms | 402 KiB | 5 Q