PHP：如何通过指定从较大的数组中提取的一组键值来创建过滤的数组？

Question

How can I create a smaller, filtered array based on a larger array. For example, this is the larger array:

$large_array = array(
    'user_email' => array(
        'required' => true,
        'email' => true,
        'max' => 200,
        'unique' => 'users'),
    'password' => array(
        'required' => true,
        'min' => 6,
        'max' => 20),
    'password_again' => array(
        'required' => true,
        'matches' => 'password'),
    'name_first' => array(
        'required' => false,
        'min' => 2,
        'max' => 64),
    'name_last' => array(
        'required' => false,
        'min' => 2,
        'max' => 64));

I want to create a filtered array based on the 'user_email' and 'name_first' keys from the large array. This filtered array would end up looking like this:

$filtered_array = array(
    'user_email' => array(
        'required' => true,
        'email' => true,
        'max' => 200,
        'unique' => 'users'),
    'name_first' => array(
        'required' => false,
        'min' => 2,
        'max' => 64);

What's the best way to do this in PHP? I'm trying to get a function that takes a set of keys and the $large_array to create the $filtered_array.

Answer 1

Use array_filter with the ARRAY_FILTER_USE_KEY flag.

Like so:

$filtered_array = array_filter($myarr, function($key){
    $keys = array("key1", "key2");
    return in_array($key, $keys);
}, ARRAY_FILTER_USE_KEY);

If your php version is < 5.6.0 you won't be able to use the ARRAY_FILTER_USE_KEY flag and if your php version is < 5.3.0 you won't be able to use the anonymous function syntax, however you can simply create a named function and pass that name as a string for the callback parameter.

Alternatively, this should do the same thing:

function ($arr, $keys)
{
    $newArr = array();

    foreach($arr as $key => $val)
    {
        if(in_array($key, $keys))
            $newArr[$key] = $val;
    }

    return $newArr;
}