1-100 prime (prime) and

Also known prime number prime number. Is a natural number greater than 1, except 1 and itself, the other can not be called a natural number divisible prime number;

Otherwise known as composite numbers: The basic idea of ​​judgment

In general the field, for positive integer n, if all removed by an integer between 2 and are not divisible, then n is a prime number.
Prime number not less than 2 is not divisible by the number other than 1 and is itself

 

 1 $arr = array();
 2 
 3     for ($i=2; $i<=100; $i++){
 4         $str = false;
 5         for ($j=2; $i<=4 ? $j<$i : $j<=$i/2; $j++){
 6 
 7             if ($i % $j == 0){
 8                 $str = false;
 9                 break ;
10             }else{
11 
12                 $str = true;
13 
14             }
15 
16         }
17 
18         if($str){
19             array_push($arr,$i);
20         }
21 
22     }
23     echo print_r($arr);

PHP

$arr = array();

	for ($i=2; $i<=100; $i++){
	    $str = false;
	    for ($j=2; $i<=4 ? $j<$i : $j<=$i/2; $j++){

	        if ($i % $j == 0){
	            $str = false;
	            break ;
	        }else{

	            $str = true;

	        }

	    }

	    if($str){
	        array_push($arr,$i);
	    }

	}
	echo print_r($arr);