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run code in 200+ PHP versions simultaneously
<?php /** * @property stdClass $x * @property stdClass $y */ class C { private $buffer = array(); function __get($key) { if (array_key_exists($key, $this->buffer)) { return $this->buffer[$key]; } $f = 'calc_' . $key; $v = $this->$f(); if (array_key_exists($key, $this->buffer)) { return $this->buffer[$key]; } return $this->buffer[$key] = $v; } function calc_x() {print __METHOD__ . "\n"; $x = new stdClass; $x->y = $this->__get('y'); return $x; } function calc_y() {print __METHOD__ . "\n"; $y = new stdClass; // Set a stub to avoid infinite recursion. $this->buffer['y'] = $y; $y->x = $this->__get('x'); return $y; } } $c = new C; $x = $c->x; $y = $c->y; var_dump($x->y === $y, $y->x === $x); print "\n"; $c = new C; $y = $c->y; $x = $c->x; var_dump($x->y === $y, $y->x === $x);
based on Nb3VF
Output for 5.5.0 - 7.4.0
C::calc_x C::calc_y C::calc_x bool(true) bool(true) C::calc_y C::calc_x bool(true) bool(true)