如何计算PHP中的移动平均值（数组前n个元素的平均值）？

PHP has the function of trader_sma for calculating the moving average. Since the concept is simple, I tried to write a function to do so. For this purpose, I kept the last n elements in an array during a loop, as

function sma($array,$period){
    foreach($array as $element){
        $c[$element[0]]=$element[1];
            if(count($c)>$period){
                $garbage = array_shift($c);
                $average = array_sum($c)/$period;
                $result[]=array($element[0],$average);
            }
    }
return($result);
}

where the input and output arrays have the structure of array(array(['x'],['y']))

The function works perfectly, but when having large inputs, the PHP trader_sma is 10 times faster than my function. Therefore, I came to the conclusion that my function is not the correct or at least the efficiency way.

Do you have any suggestion?