3v4l.org

run code in 300+ PHP versions simultaneously
<?php $makefoo = true; /* 我们不能在处调用foo()函数， 因为它还不存在，但可以调用bar()函数。*/ bar(); if ($makefoo) { function foo() { echo "I don't exist until program execution reaches me.\n"; } } /* 现在我们可以安全调用函数 foo()了， 因为 $makefoo 值为真 */ if ($makefoo) foo(); function bar() { echo "I exist immediately upon program start.\n"; } ?>
Output for 4.3.0 - 4.3.11, 4.4.0 - 4.4.9, 5.0.0 - 5.0.5, 5.1.0 - 5.1.6, 5.2.0 - 5.2.17, 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 - 8.1.28, 8.2.0 - 8.2.18, 8.3.0 - 8.3.7
I exist immediately upon program start. I don't exist until program execution reaches me.
preferences:
304.92 ms | 406 KiB | 457 Q