3v4l.org

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<?php $bad=array(); $good=array(); $a=['a','b','c']; $b=['c','d','e']; $bad += $a; $bad += $b; print_r($bad); $good = array_unique(array_merge($good, $a)); $good = array_unique(array_merge($good, $b)); print_r($good);
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 - 8.1.33, 8.2.0 - 8.2.29, 8.3.0 - 8.3.26, 8.4.1 - 8.4.14
Array ( [0] => a [1] => b [2] => c ) Array ( [0] => a [1] => b [2] => c [4] => d [5] => e )
preferences:
169.65 ms | 408 KiB | 5 Q