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<?php $a=range(1, 500); foreach($a as $k=>$v) { } var_dump(memory_get_peak_usage()); $a=range(1, 500); foreach($a as $k=>$v) { echo $v; } var_dump(memory_get_peak_usage()); foreach($a as $k=>$v) { $a[$k]++; } var_dump(memory_get_peak_usage());

preferences:
39.64 ms | 402 KiB | 5 Q