PHP 函数的函数指针的优点是什么？

function sum($a, $b) {
  return $a + $b;
}

function apply_function($x, $y, $function) {
  return $function($x, $y);
}

$result = apply_function(5, 10, 'sum');
echo $result; // 输出: 15

function multi_filter($array, ...$callbacks) {
  return array_filter($array, function($element) use ($callbacks) {
    foreach ($callbacks as $callback) {
      if (!$callback($element)) {
        return false;
      }
    }
    return true;
  });
}

$array = [1, 2, 3, 4, 5, 6];
$filtered = multi_filter($array, function($element) {
  return $element % 2 === 0;
}, function($element) {
  return $element < 5;
});

print_r($filtered); // 输出: [2, 4]

$callback = function() {
  echo "This function was called later";
};

// 在稍后的时间调用函数指针
call_user_func($callback);

// 使用匿名函数创建数组映射函数
$array = ['a', 'b', 'c'];
$mapped = array_map(function($item) {
  return strtoupper($item);
}, $array);

print_r($mapped); // 输出: ['A', 'B', 'C']