Looking for a way to find prime numbers in php? I wfound one perl solution here, but it wasn’t perl magic – it was power of regular expressions.

Please find code below which will be self-explanatory.


<?php

/**
* Function checks if given number is prime
*
* @param integer $n
* @return boolean
*/
function isPrime($n) {
return (!preg_match(‘/^1?$|^(11+?)\1+$/x’, str_repeat(’1′, intval($n)))) ;
}

for ($n=0;$n<100;$n++) {
echo “Number {$n} is “.(isPrime($n) ? ‘prime’ : ‘not prime’).”<br/>\n”;
}

?>