PHP program to calculate factors of a given number

<?php
//We Define a function that gets
//an argument and return the factors
//of the number it got.
// Function definition
function factors_of_a_number($n)
{
    if ($n == 0)
    {
        // because we cannot divide 0/0 does not exist
        echo "Zero has no factors";
    }
    else
    {
        // format our answer to look good.
        print_r("The factors of $n are {");
        //We will use a for loop to loop through
        // each number in the series  1 to our number $n
        // dividing $n by each number
        for ($x = 1;$x <= $n;$x++)
        {
            // the modulus operator
            // helps us get the remainder of each division
            $factor = $n % $x;

            //we will check to see which number return a 0 as reminder
            // the we echo that number because it is a factor of our number $n.
            if ($factor == 0)
            {
                print_r($x . ",");
            }
        }
        print_r("}");
    }
}
print_r(factors_of_a_number(0) . "\n");
print_r(factors_of_a_number(50) . "\n");
?>

Output
Zero has no factors
The factors of 50 are {1,2,5,10,25,50,}