## Thursday, 27 January 2011

### Calculate prime numbers using PHP

Simply create a file named primeNumberCalculator.php. Copy following text in it.

You need a web server supporting php scripting.
Place the file where your http web server see it. e.g: /var/www

Open the file in a web browser. e.g: http://localhost/primeNumberCalculator.php

```<html>
<body>

<h2>PHP Prime number calculator</h2>
How many primes?: <input type="text" name="count" />
<input type="submit" value="Submit" />
</form>
<?php

// How many prime numbers are we going to calculate:
\$count=\$_GET["count"];
if (\$count == "") {
\$count = 10;  // Default value
}

// We show the first prime number:
\$prime_array=array("2");
echo \$prime_array[0];
echo " ";

\$total=1; // prime number array length.
\$number = 3; // current number we are going to test for primality.

while ( \$i<\$count ) {
\$index=0;
\$is_prime="true";
\$max = floor(sqrt(\$number));
\$n = \$prime_array[\$index];
while((\$n <= \$max) && (\$is_prime == "true")) {
if ((\$number % \$n) == 0) {
\$is_prime="false";
}
\$index++;
\$n = \$prime_array[\$index];
}
if (\$is_prime=="true") {
echo " " . \$number;
\$prime_array[\$total] = \$number;
\$total++;
\$i++;
}

\$number += 2;
}

?>

</body>
</html>
```