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<?php $amount = 4; @$a[5] += $amount; print_r($a); $b[6] = ($b[6] ?? 0) + $amount; print_r($b); @$c->x[5] += $amount; print_r($c); $d[3] = (isset($d[3]) ? $d[3] : 0) + $amount; print_r($d);

preferences:
53.83 ms | 402 KiB | 5 Q