Added solution in PHP language

[sarvar-akbarov]

class Solution {

    /**
     * @param Integer[] $nums
     * @param Integer $pivot
     * @return Integer[]
     */
    function pivotArray($nums, $pivot) {
        $result = [];

        $countPivots = 0;

        foreach($nums as $key => $num){
            if($num < $pivot){
                $result[] = $num;
                unset($nums[$key]);
            }elseif($num == $pivot){
                $countPivots++;
                unset($nums[$key]);
            }
        }

        while($countPivots--){
            $result[] = $pivot;
        }

        foreach($nums as $num){
            $result[] = $num;
        }

        return $result;
    }
}