3v4l.org

run code in 300+ PHP versions simultaneously
<?php $source = ["a" => 1, "b" => 2, "c" => 3]; echo json_encode(["d" => 4, "b" => 10] + $source) . PHP_EOL; echo json_encode(array_merge($source, ["d" => 4, "b" => 10])) . PHP_EOL;
Output for 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
{"d":4,"b":10,"a":1,"c":3} {"a":1,"b":10,"c":3,"d":4}
preferences:
128.92 ms | 407 KiB | 5 Q