Question

function parent($key)
{
     function son()
     {
         global $key;
     }
}

I want to achieve this:

2. son can access the $key of parent

As it’s quite a simple function,I don’t want to change parent into a class

OK,I’ve been told that function are global anyway.Is there a way for son to get $key of parent then?

Answer 1

Since PHP 5.3 you can do:

function parent($key) {
    $son = function() use (&$key) {
        var_dump($key);
    };
    $son();
}
parent('foo');

About usort — are you looking for something like this?

$key = 'foo';
$arr = array(
    array(0, 'foo' => 1),
    array(1, 'foo' => 4),
    array(2, 'foo' => -2),
);

usort($arr, function ($a, $b) use (&$key) {
    $a = $a[$key];
    $b = $b[$key];
    if ($a == $b) return 0;
    return ($a < $b) ? -1 : 1;
});

var_dump($arr);