3v4l.org

run code in 300+ PHP versions simultaneously
<?php $a = ['a' => 1, 2 => 2, '3' => 3 => '3']; echo array_keys($a);
Output for 5.4.0 - 5.4.23
Parse error: syntax error, unexpected '=>' (T_DOUBLE_ARROW), expecting ']' in /in/HXkYm on line 3
Process exited with code 255.
Output for 5.3.0 - 5.3.28
Parse error: syntax error, unexpected '[' in /in/HXkYm on line 3
Process exited with code 255.
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179.32 ms | 1395 KiB | 60 Q