计算某个键名出现在多个数组中的次数？

Question

How may I count the times a key shows up in a multi-array?

In the below example, weight should return 2, and reps 4. Does PHP have a built-in function for this?

                [0] => Array
                    (
                        [0] => Array
                            (
                                [weight] => 317.51474856007
                                [reps] => 10
                            )

                        [1] => Array
                            (
                                [weight] => 50
                                [reps] => 10
                            )

                        [2] => Array
                            (
                                [reps] => 10
                            )

                        [3] => Array
                            (
                                [reps] => 10
                            )

                    )

Answer 1

Try this one liner using array_walk_recursive():

Given your array, $arr

array_walk_recursive($arr, function($v, $k)use(&$count){if(array_key_exists($k, $count))$count[$k]++;else $count[$k]=1;},$count=array());
print_r($count);

See demo

or the old fashioned way:

$count = array();
foreach ($arr as $ar){
    foreach ($ar as $k=>$v){
        if (array_key_exists($k, $count)){
            $count[$k]++;
        }
        else{
            $count[$k] = 1;
        }
    }
}
print_r($count);

See demo

Output:

Array
(
    [weight] => 2
    [reps] => 4
)