PHP Program to Check Prime Number

What is Prime Number?

A positive integer that is divisible only by itself and 1.

Tips: It is recommended to use our online Prime Numbers calculator for better understanding.

Examples

The following table provides few examples of prime numbers.

NumberDivisorResult
131, 13Prime Number
151, 3, 5, 15Not a Prime Number
471, 47Prime Number

Using for loop

In the following example, we will check whether the given number (7) is a Prime number or not using for loop.

Example

PHP Compiler
<?php $num = 7; $count = 0; for($i=1; $i<=$num; $i++) { if($num % $i == 0) $count++; } if($count == 2) echo "$num is a prime number"; else echo "$num is not a prime number"; ?>

Using while loop

In the following example, we will check whether the given number (7) is a Prime number or not using while loop.

Example

PHP Compiler
<?php $num = 7; $i = 1; $count = 0; while($num >= $i) { if($num % $i == 0) $count++; $i++; } if($count == 2) echo "$num is a prime number"; else echo "$num is not a prime number"; ?>

Using do while loop

In the following example, we will check whether the given number (7) is a Prime number or not using do while loop.

Example

PHP Compiler
<?php $num = 7; $i = 1; $count = 0; do{ if($num % $i == 0) $count++; $i++; }while($i<= $num); if($count == 2) echo "$num is a prime number"; else echo "$num is not a prime number"; ?>

Prime Numbers between the Given Range

In the following example, we will find all the Prime numbers between 1 and 20.

Example

PHP Compiler
<?php $start = 1; $end = 20; $count = 0; $flag = 0; $i = 1; echo "Prime numbers between $start and $end: <br>"; for($start=$start; $start<=$end; $start++) { for($i=1; $i<=$start; $i++) { if($start % $i == 0) $count++; } if($count == 2) { $flag = 1; echo "$start "; } $count = 0; } if($flag == 0) echo "There is no Prime numbers between the given series"; ?>

Check Whether the Given Number is Prime or Composite

In the following example, we will check whether the given number is a Prime number or Composite number.

Example

PHP Compiler
<?php $num = 11; $count = 0; for($i=1; $i<=$num; $i++) { if($num % $i == 0) $count++; } if($count == 2) echo "$num is a prime number"; else echo "$num is a composite number"; ?>

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