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# Check A Number is Prime or Not in PHP

## How to Check a Number is Prime or Not in PHP

If you are looking to check a number is prime in PHP then you are at the right place because here we will show whether a number is prime or not using PHP.

Here I am just showing you a program to check prime number in php. The technique that I am going to show you very simple and simple but quite potent and here you will also find how to alter and personalize these codes readily according to your need.

### What is Prime Number?

A Number that is divisible by itself as well as 1 then it called given number is Prime Number. For eg- in the event that you take the number 11, it can only be divided to acquire a complete number if it is divided by 1 or 11. If any other number is used subsequently a percentage is obviously found.

```<?php
if(isset(\$_POST['submit']))
{
//retrieve number form POST submission
\$num=\$_POST['num'];
\$primeFlag=0;

//if not perfectly divisible by any,
//number is prime
for(\$i=2;\$i<\$num;\$i++)
{
\$primeFlag=0;
if((\$num%\$i)==0)
{
break;
}
\$primeFlag=1;
}
if(\$primeFlag==1)
{
echo " \$num  is Prime Number";
}
else
{
echo "\$num is not  Prime number";
}
}
?>
<!DOCTYPE html?>
<html?>
<title>Write a Program to check Prime Number</title>
<body>
<form method="post">

<table>
<tr>
<td><input type="text" name="num"></td>
</tr>
<tr>
<td colspan="2" align="center">
<input type="submit" name="submit" value="submit">
</td>
</tr>
</table>
</form>
</body>
</html>
```
Output:

### Check Prime Number in Array

```<?php
if(isset(\$_POST['submit']))
{
//retrieve number form POST submission
//convert to array by splittiing on comma
\$numStr=\$_POST['num'];
\$numArr=explode(",",\$_POST['num']);
\$primes=array();
\$primeFlag=0;

//iterate over array
//get absolute values of each number
foreach(\$numArr as \$n)
{
\$n=trim(abs(\$n));
//test each number for prime-ness:
//check the number by dividing it
//by all the numbers between 2 and itself
//if not perfectly divisible by any,
//number is prime
for(\$i=2;\$i<\$n;\$i++)
{
\$primeFlag=0;
if((\$n%\$i)==0)
{
break;
}
\$primeFlag=1;
}
//if prime add to output array
if(\$primeFlag==1)
{
array_push(\$primes,\$n);
}
}

//check if any primes number were found then sort and remove duplicate from array and prit
if(count(\$primes)>0)
{
\$primes=array_unique(\$primes);
sort(\$primes);
echo "The following numbers are prime : ".implode(\$primes," ");
}
else
{
echo "No Prime numbers found";
}

}
?>
<!DOCTYPE html>
<html>
<title>check prime number</title>
<body>
<form method="post">

<table>
<caption><h3>Project : Prime Number Tester</h3></caption>
<tr>
<td>Enter a list of numbers, Seperated by Commas</td>
<td><input type="text" name="num"></td>
</tr>
<tr>
<td colspan="2" align="center">
<input type="submit" name="submit" value="submit">
</td>
</tr>
</table>
</form>
</body>
</html>
```