Question 171475 in PHP Question posted in
Official manual can be found here.

Does the PHP null coalescing operator prevent errors?

I’m getting the error "Undefined array key "name" in the following code:

if ($arr & $arr['name']??'')

Shouldn’t the null coalescing operator prevent that error if the array key doesn’t exist??

I tried using isset() instead and it did not return an error. But what gives?

I’ve used the null coalescing operator loads before and never had any problems with it. I don’t understand what is different about this code?

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2

Answers


  1. 0

    The null coalesce operator does not produce a warning/error.

    As stated in https://www.php.net/manual/en/language.operators.comparison.php#language.operators.comparison.coalesce, the coalesce is identical to using isset(). You have a & instead of && in the code.

    <?php
// Example usage for: Null Coalesce Operator
$action = $_POST['action'] ?? 'default';

// The above is identical to this if/else statement
if (isset($_POST['action'])) {
    $action = $_POST['action'];
} else {
    $action = 'default';
}
?>
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  2. 0

    Regardless of the use of & versus &&, those operators have a higher precedence than the ?? operator. So this:

    if ($arr && $arr['name'] ?? '')

    Evaluates to this:

    if (($arr && $arr['name']) ?? '')

    Which means PHP tries first to evaluate $arr['name'] outside the context of the null coalesce, so you get the notice. You can force the desired precedence with explicit parens:

    if ($arr && ($arr['name'] ?? ''))

    That said, the explicit check for $arr is generally not needed when you use null coalesce, so what you probably want is simply:

    if ($arr['name'] ?? '')

    Which basically means, "if a value is present and not empty."

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