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.

<?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

Example:

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

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