Prime Number

A number which is only divisible by 1 and itself is called prime number. Numbers 2, 3, 5, 7, 11, 13, 17, etc. are prime numbers.

• 2 is the only even prime number.
• It is a natural number greater than 1 and so 0 and 1 are not prime numbers.

Prime number in PHP

Example:

Here is the Program to list the first 15 prime numbers.

1. <?php  
2. $count = 0;  
3. $num = 2;  
4. while ($count < 15 )  
5. {  
6. $div_count=0;  
7. for ( $i=1; $i<=$num; $i++)  
8. {  
9. if (($num%$i)==0)  
10. {  
11. $div_count++;  
12. }  
13. }  
14. if ($div_count<3)  
15. {  
16. echo $num." , ";  
17. $count=$count+1;  
18. }  
19. $num=$num+1;  
20. }  
21. ?>  

Output:

8. Modules and PHP Abstract class | Build a CMS using OOP PHP CMS tutorial MVC [2020]

Prime Number using Form in PHP

Example:

We'll show a form, which will check whether a number is prime or not.

1. <form method="post">  
2. Enter a Number: <input type="text" name="input"><br><br>  
3. <input type="submit" name="submit" value="Submit">  
4. </form>  
5. <?php  
6. if($_POST)  
7. {  
8.     $input=$_POST['input'];  
9.     for ($i = 2; $i <= $input-1; $i++) {  
10.       if ($input % $i == 0) {  
11.       $value= True;  
12.       }  
13. }  
14. if (isset($value) && $value) {  
15.      echo 'The Number '. $input . ' is not prime';  
16. }  else {  
17.    echo 'The Number '. $input . ' is prime';  
18.    }   
19. }  
20. ?>  

Output:

On entering number 12, we get the following output. It states that 12 is not a prime number.

On entering number 97, we get the following output. It states that 97 is a prime number.