3v4l.org

run code in 300+ PHP versions simultaneously
<?php $arr = [1 => 1, 3 => 3]; // [1 => 1, 2 => 3] will print both keys foreach($arr as $key => &$val) { // without & will print both keys echo "See key {$key}\n"; $arr[0] = 0; // without this line will print both keys unset($arr[0]); }
Output for 5.6.38, 7.0.33, 7.1.0 - 7.1.25, 7.2.11 - 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 - 8.3.25, 8.4.1 - 8.4.12
See key 1 See key 3
Output for 7.2.0 - 7.2.10
See key 1

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140.6 ms | 407 KiB | 5 Q