PHP Program to Count 1's in a sorted binary array

<?php
// PHP program to count one's in a
// boolean array

/* Returns counts of 1's in arr[low..high].
The array is assumed to be sorted in 
non-increasing order */
function countOnes( $arr, $low, $high)
{
    if ($high >= $low)
    {
        // get the middle index
        $mid = $low + ($high - $low)/2;
    
        // check if the element at middle
        // index is last 1
        if ( ($mid == $high or $arr[$mid+1] == 0) 
                           and ($arr[$mid] == 1))
            return $mid+1;
    
        // If element is not last 1, recur for 
        // right side
        if ($arr[$mid] == 1)
            return countOnes($arr, ($mid + 1),
                                          $high);
    
        // else recur for left side
        return countOnes($arr, $low, ($mid -1));
    }
    
    return 0;
}

/* Driver code */
$arr = array(1, 1, 1, 1, 0, 0, 0);
$n = count($arr);
echo "Count of 1's in given array is " , 
                      countOnes($arr, 0, $n-1);

// This code is contributed by anuj_67.
?>