Password Generator by PHP #PHP

<html>
 <body>
  <table border="1" align="center">
   <form method="post" action="passgene.php">
   <tr><td>文字数</td><td><input type="text" size="10" name="chara_num"></td></tr>
   <tr><td>アルファベット小文字</td><td><input type="checkbox" name="small_letter"></td></tr>
   <tr><td>アルファベット大文字</td><td><input type="checkbox" name="capital_letter"></td></tr>
   <tr><td>数字</td><td><input type="checkbox" name="numeral_letter"></td></tr>
   <tr><td>特殊文字</td><td><input type="checkbox" name="special_letter"></td></tr>
   <tr slign="center"><td colspan="2"><input type="submit"></td></tr>
   </form>
  </table>

<?php
$num_char  = $HTTP_POST_VARS["chara_num"];
$sm_letter = $HTTP_POST_VARS["small_letter"];
$ca_letter = $HTTP_POST_VARS["capital_letter"];
$nu_letter = $HTTP_POST_VARS["numeral_letter"];
$sp_letter = $HTTP_POST_VARS["special_letter"];
$strin1 = "a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z,";
$strin2 = "A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z,";
$strin3 = "1,2,3,4,5,6,7,8,9,0,";
$strin4 = ">,<,#,$,%,&,-,/,[,],!,(,),=,~,^,|,{,},@,";
$judge  = 0;
$selected_array;
if($sm_letter=="on"){     $judge += 1;    }
if($ca_letter=="on"){     $judge += 10;   }
if($nu_letter=="on"){     $judge += 100;  }
if($sp_letter=="on"){ $judge += 1000; }
if($judge==1){
   $selected_array = $strin1;
}else if($judge==10){
   $selected_array = $strin2;
}else if($judge==11){
   $selected_array = $strin1.$strin2;
}else if($judge==100){
   $selected_array = $strin3;
}else if($judge==101){
   $selected_array = $strin3.$strin1;
}else if($judge==110){
   $selected_array = $strin3.$strin2;
}else if($judge==111){
   $selected_array = $strin3.$strin2.$strin1;
}else if($judge==1000){
   $selected_array = $strin4;
}else if($judge==1001){
   $selected_array = $strin4.$strin1;
}else if($judge==1010){
   $selected_array = $strin4.$strin2;
}else if($judge==1011){
   $selected_array = $strin4.$strin2.$strin1;
}else if($judge==1100){
   $selected_array = $strin4.$strin3;
}else if($judge==1101){
   $selected_array = $strin4.$strin3.$strin1;
}else if($judge==1110){
   $selected_array = $strin4.$strin3.$strin2;
}else if($judge==1111){
   $selected_array = $strin4.$strin3.$strin2.$strin1;
}

$strarray = explode(",",$selected_array,-1);
if(!$strarray){
   $str = "";
}else{
   for ($i = 0, $str = null; $i < $num_char; $i++) {
     $str .= $strarray[array_rand($strarray, 1)];
   }
}
?>

  <div align="center"><font size="7" color="Blue"><?php print($str); ?></font</div>
 </body>
</html>