Prime Numbers Generators

<?php



function prime0($n) {
    // Lets time ourself.
    $time_start = microtime(true);

    echo "
    <style>.test-table {float:left;} .test-table td {border:solid 1px #000;}</style>
    <div>Prime Numbers = $n<br><br></div>
    <table class='test-table'>
    <tr><td colspan='2'>Dan Huckson prime0</td></tr>
    <tr><td>Count</td><td>Prime Number</td></tr>";

    $count = 0;
    for ($x = 2; $count < $n; $x++) {
        $i = 2;
        $prime = true;
        $sqrt = sqrt($x);
        if ($x > 2)
            while ($i <= $sqrt)
                if ($x%$i++ == 0) {
                    $prime = false;
                    break;
                }

        if ($prime) echo "<tr><td>".(++$count)."</td><td>".($x)."</td></tr>";
    }

    echo "
    </table>
    <div>".(microtime(true) - $time_start)." seconds.</div>";
}

function prime1($n) {
    $time_start = microtime(true);

    echo "
    <style>.test-table {float:left;} .test-table td {border:solid 1px #000;}</style>
    <table class='test-table'>
    <tr><td colspan='2'>Dan Huckson prime1</td></tr>
    <tr><td>Count</td><td>Prime Number</td></tr>";

    $count = 0;
    $primes = array();

    for ($x = 2; $count < $n; $x++) {
        $prime = true;

        if ($x > 2) {
            foreach ($primes as $num) {
                if ($x%$num == 0) {
                    $prime = false;
                    break;
                }
            }
        }

        if ($prime) echo "<tr><td>".(++$count)."</td><td>".($primes[] = $x)."</td></tr>";
    }


    echo "
    </table>
    <div>".(microtime(true) - $time_start)." seconds.</div>";
}

function prime2($n) {
    // $n equals the number of prime numbers to proccess.

    // Lets time ourself.
    $time_start = microtime(true);

    // Display output in a table and include some styling.
    echo "
    <style>.test-table {float:left;} .test-table td {border:solid 1px #000;}</style>
    <table class='test-table'>
    <tr><td colspan='2'>Dan Huckson prime2</td></tr>
    <tr><td>Count</td><td>Prime Number</td></tr>";

    $count=0; // Prime numbers processed, or index counter.

    // We will continue to loop while our current,
    // $count (processed prime numbers) < $n (number of prime numbers to proccess) .
    // $i holds the current number being tested.
    // We are starting at 2, which will be our first prime number and continue to we find $n prime numbers.
    for ($i=2; $count < $n ; $i++) {
        // Set the result to true and change it to false if the current number ($i) is not a prime number.
        $result = TRUE;

        // Loop through all numbers from 2 to ($i/2 + 1) or (half of $i + 1).
        // If $i is not a prime number the loop is termanated by breaking out of the loop.
        $x = $i/2+1;
        for ($j=2; $j<$x; $j++) {
            if (!($i%$j)) { // If we have no remainder the number is not a prime number.
                $result=FALSE; // Set result to false not a prime number.
                break; // Save some CPU cycles, no need to continue looping if number is not prime a number.
            }
        }
        if ($result) // If $result is true ($i) is a prime number, update count and display results.
            echo "<tr><td>".(++$count)."</td><td>$i</td></tr>";
    }

    // All done, Calculate and display total run time.
    echo "
    </table>
    <div>".(microtime(true) - $time_start)." seconds.</div>";
}

function prime3($n) {
    // $n equals the number of prime numbers to proccess.

    // Lets time ourself.
    $time_start = microtime(true);

    echo "
    <style>.test-table {float:left;} .test-table td {border:solid 1px #000;}</style>

    <table class='test-table'>
    <tr><td colspan='2'>Dan Huckson prime3</td></tr>
    <tr><td>Count</td><td>Prime Number</td></tr>";

    $count=0;
    for ($i=2; $count < $n; $i++) {
        if (!gmp_intval(gmp_mod(gmp_add(gmp_fact(($i-1)),1),$i)))
            echo "<tr><td>".(++$count)."</td><td>$i</td></tr>";
    }

    echo "
    </table>
    <div>".(microtime(true) - $time_start)." seconds.</div>";
}


function prime4($n) {
    $time_start = microtime(true);

    $total = 0;
    echo "
    <style>.test-table {float:left;} .test-table td {border:solid 1px #000;}</style>
    <table class='test-table'>
    <tr><td colspan='2'>Geoff</td></tr>
    <tr><td>Count</td><td>Prime Number</td></tr>";

    for ($x = 1; $total < $n; $x++) {
        $count = 2;
        for ($y=1; $y <= $x; $y++) {
            if (!($x % $y) && !($count--)) break;
        }
        if(!$count) {
            echo "<tr><td>".(++$total)."</td><td>$x</td></tr>";
        }
    }
    echo "
    </table>
    <div>".(microtime(true) - $time_start)." seconds.</div>";
}

set_time_limit(0);
echo '
<!DOCTYPE html>
<html>
    <head>
        <meta charset="UTF-8">
        <title></title>
    </head>
    <body>';
        prime0(1000);
        prime1(1000);
        prime2(1000);
        prime3(1000);
        prime4(1000);
    echo '
    </body>
</html>';