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This script uses Sieve of Erastothenes to find all the prime up to a number
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<?php
//Made by Chao Xu
//http://webdevlogs.com/
function esprime($limit){
$sqrtlimit = sqrt($limit);
$range = 0;
while($range<$limit){
$i .= '11';
$range+=2;
}
$n = 2;
while($n < $sqrtlimit){
if ($i[$n]){
$sqn = $n*$n;
$k = $sqn;
$i[$k]=0;
while($k<=$limit){
$k += $n;
$i[$k]=0;
}
}
++$n;
}
$n = 1;
while($n<$limit){
if($i[$n]) $primes[] = $n;
$n+=2;
}
if($limit>=2) $primes[0] = 2;
return $primes;
}
?> | |
It returns an array of all prime number below an the argument.
| <?php
esprime(6);
//return array(2,3,5);
?> | |
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