One common use case for the @ operator, is when "destructuring" array members into variables. In some cases, you can't know if the member will be available, but it's not important if it's missing. In that case, you can silence the warning.

$array = ['apple', 'pear']; @list($mainFruit, $secondaryFruit, $tertiaryFruit);

Since I suppress the warning that would occur due to the third member not being present, the program will continue executing instead of halting.

    $a = 5;
    $b = fn ($c) => $a * $b;
    print($b(2)); // 10
    print($b(4)); // 20