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>
<form name="input" action="primeNumberCalculator.php" method="get">
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.
$i=1; // We start with 1 because first prime is already printed.
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>
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