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run code in 300+ PHP versions simultaneously
<?php // given: $undef = 'a'; unset($undef); $null = NULL; $false = FALSE; $true = TRUE; // these operations: var_dump(isset($undef)); var_dump(empty($undef)); var_dump(array_key_exists('undef', $GLOBALS)); // "defined" below
Output for 4.3.0 - 4.3.11, 4.4.0 - 4.4.9, 5.0.0 - 5.0.5, 5.1.1 - 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 - 5.6.28, 7.0.5 - 7.0.20, 7.1.0 - 7.1.25, 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
bool(false) bool(true) bool(false)
Output for 7.0.0 - 7.0.4
bool(false) bool(true) bool(true)
Output for 5.1.0
Fatal error: fatal flex scanner internal error--end of buffer missed in /in/j1lOE on line 13
Process exited with code 255.

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