- var_dump: documentation ( source)
<?php
$maybeHasAB = ['a value'];
$defaultAB = ['a default', 'b default'];
[$a, $b] = ($maybeHasAB + $defaultAB);
var_dump($a, $b);
$a = $maybeHasAB[0] ?? $defaultAB[0];
$b = $maybeHasAB[1] ?? $defaultAB[1];
var_dump($a, $b);