PHP 三元运算 ?? 与 ?:


// $c = $a ?? $b;  等效  $c = isset($a) ? $a : $b;
// $c = $a ?: $b;  等效  $c = $a ? $a : $b;

$a = 'a';
$b = 'b';

$c = $a ?? $b; // a
$c = $a ?: $b; // a


$a = false;
$b = 'b';

$c = $a ?? $b; // false
$c = $a ?: $b; // b

Practice makes perfect.

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