PHP function Exercises: Check whether a number is prime or not

Last update on December 20 2024 10:19:08 (UTC/GMT +8 hours)

Write a PHP function to check whether a number is prime or not.

Note: A prime number (or a prime) is a natural number greater than 1 that has no positive divisors other than 1 and itself.

Visual Presentation:

Sample Solution:

PHP Code:

<?php
// Function to check if a number is prime
function IsPrime($n)
{
    // Loop through all numbers from 2 to n-1
    for ($x = 2; $x < $n; $x++)
    {
        // If n is divisible by any number other than 1 and itself,
        // it's not prime, so return 0
        if ($n % $x == 0)
        {
            return 0;
        }
    }
    // If no divisor found, n is prime, so return 1
    return 1;
}

// Call the IsPrime function to check if 3 is prime
$a = IsPrime(3);

// Check the return value and print the result
if ($a == 0)
    echo 'This is not a Prime Number.....' . "\n";
else
    echo 'This is a Prime Number..' . "\n";
?>

Output:

This is a Prime Number..

Explanation:

In the exercise above,

• Define a function named "IsPrime()" which takes an integer parameter '$n'.
• Inside the function, there's a loop that iterates from 2 to one less than '$n'. This loop checks for divisors of '$n'.
• If '$n' is divisible by any number other than 1 and itself, the function returns 0, indicating that the number is not prime.
• If no divisor is found in the loop, the function returns 1, indicating that the number is prime.
• Outside the function, the "IsPrime()" function is called with an argument of 3, and the result is stored in the variable '$a'.
• The code then checks the value of '$a' and prints whether 3 is a prime number or not.

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