3v4l.org

run code in 300+ PHP versions simultaneously
<?php $a = array('one', 'two', 'three', 'four'); $i = sizeof($a); $j = 0; $array=""; for($j=0;$j<$i-1;$j++) { $array[] = $a[$j]." ".$a[$j+1]; } print_r($array);
Output for 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 - 8.1.27, 8.2.0 - 8.2.17, 8.3.0 - 8.3.4
Fatal error: Uncaught Error: [] operator not supported for strings in /in/skUv5:8 Stack trace: #0 {main} thrown in /in/skUv5 on line 8
Process exited with code 255.
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
Array ( [0] => one two [1] => two three [2] => three four )

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276.35 ms | 403 KiB | 456 Q