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run code in 300+ PHP versions simultaneously
<?php $from = range(1, 2500); $to = array_combine(range(2501, 5000), range(2501, 5000)); foreach($from as $i => $v) { $to = array_merge($from, array($i => $v)); echo $i."\n"; }

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43.35 ms | 402 KiB | 5 Q