Perfect number program in PHP

In this post, you will learn how to check for the perfect number using the PHP programming language. The perfect number program is generally asked in PHP coding tests and interviews.

A perfect number is a positive integer that is equal to the sum of its positive divisors, excluding the number itself. In other words, a number whose sum of factors is equal to the number, excluding the number itself is called a perfect number.

The sum of divisors of a number, excluding the number itself, is called its aliquot sum, so a perfect number is one that is equal to its aliquot sum. For example, 6 has divisors 1, 2 and 3, and 1 + 2 + 3 = 6, so 6 is a perfect number. 6 is the first perfect number.

Perfect Number	Sum of its Divisors
6	1+2+3
28	1+2+4+7+14
496	1+2+4+8+16+31+62+124+248
8,128	1+2+4+8+16+32+64+127+254+508+1,016+2,032+4,064

Here, we have mentioned three different ways to find the perfect number in PHP.

Perfect Number Program in PHP using For loop

In the given PHP program, we have checked whether the entered number is perfect or not using the for loop.

<?php
// Perfect Number program in PHP using For Loop 
function isPerfectNumber($num)
{
    $sum = 0;
       
    // Traversing through each number
    for ($i = 1; $i < $num; $i++)
    {
        if ($num % $i == 0)
        {
            $sum = $sum + $i;
        }      
    }
    //comparing the sum with the number 
    return $sum == $num;
}
   
// Driver's code
$num = 28;
  
if (isPerfectNumber($num))
    echo $num." is perfect number.";
else
    echo $num." is not a perfect number.";
?>

Output of the above code:

28 is perfect number.

Perfect Number Program in PHP using While loop

In the given PHP program, we have checked whether the entered number is perfect or not using the while loop.

<?php
// Perfect number program in PHP using While Loop 
function isPerfectNumber($num)
{
    $sum = 0;
    $i = 1;
       
    // Traversing through each number
    while($i <= $num/2)  
    {  
        if($num % $i == 0)  
        {  
            //calculating the sum of factors  
            $sum = $sum + $i;  
        }
    $i++;  
    } 
    //comparing the sum with the number 
    return $sum == $num;
}
   
// Driver's code
$num = 496;
  
if (isPerfectNumber($num))
    echo $num." is perfect number.";
else
    echo $num." is not a perfect number.";
?>

Output of the above code:

496 is perfect number.

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