PHP program to find Prime Number

<?php  
$count = 0;  
$num = 2;  
while ($count < 15 )  
{  
$div_count=0;  
for ( $i=1; $i<=$num; $i++)  
{  
if (($num%$i)==0)  
{  
$div_count++;  
}  
}  
if ($div_count<3)  
{  
echo $num." , ";  
$count=$count+1;  
}  
$num=$num+1;  
}  
?>  

Output:
2,3,5,7,11,13,17,19,23,29,31,37,41,43,47