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.

Prime number in PHP

Example:

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

Example

                  
<?php
$count = 0;  
$num = 2;  
while ($count < 15 )  
{  
$div_count=0;  
for ( $i=1; $i<=$num; $i++)  
{  
if (($num%$i)==0)  
{  
$div_count++;  
}  
}  
if ($div_count<3)  
{  
echo $num." , ";  
$count=$count+1;  
}  
$num=$num+1;  
}                  
?>

Output

Prime Number using Form in PHP

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

Example


                    
<form method="post">  
Enter a Number: <input type="text" name="input"><br><br>  
<input type="submit" name="submit" value="Submit">  
</form>  
<?php  
<form method="post">  
    Enter a Number: <input type="text" name="input"><br><br>  
    <input type="submit" name="submit" value="Submit">  
    </form>  
    <?php  
    if($_POST)  
    {  
        $input=$_POST['input'];  
        for ($i = 2; $i <= $input-1; $i++) {  
          if ($input % $i == 0) {  
          $value= True;  
          }  
    }  
    if (isset($value) && $value) {  
         echo 'The Number '. $input . ' is not prime';  
    }  else {  
       echo 'The Number '. $input . ' is prime';  
       }   
    }  
?>

Output

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

Output