When I try to submit data it show Notice: Undefined variable: err2 in C:\xampp\htdocs\instaload\dbbl.php on line 71

Question

I am trying to developing a form using php. I already define err1,err2...err3. But When I try to submit data it show Notice: Undefined variable: err2 in C:\xampp\htdocs\instaload\dbbl.php on line 71. Other hand my data insert successfully in database but it show this notice. Please tell me how can i solve this.

This is my php code:

<?php

if($_POST)
{

$num = mysql_real_escape_string($_POST["num"]);
$amount = mysql_real_escape_string($_POST["amount"]);
$typ = mysql_real_escape_string($_POST["typ"]);
$pin = $_POST["pin"];




if(strlen($num)<="10"){
$err1=1;
}


if ($mallu<$amount){
$err2=1;
}


if ($amount<="10"){
$err3=1;
}

if ($pin!=$upin){
$err4=1;
}


  $error = $err1+$err2+$err3+$err4;


 if ($error == 0){


 ///--------------------------- CUT THE BALANCE
 $newbal = $mallu-$amount;
 $res = mysql_query("UPDATE users SET mallu='".$newbal."' WHERE      id='".$uid."'");

if($res){
echo "<div class=\"alert alert-success alert-dismissable\">
 <button type=\"button\" class=\"close\" data-dismiss=\"alert\" aria-     hidden=\"true\">&times;</button>  
 Request Send Successfully!
</div>";


mysql_query("INSERT INTO request SET rtyp='Mobile Recharge',     num='".$num."', amount='".$amount."', typ='".$typ."', usr='".$uid."',   tm='".$tm."', status='0'");


 }else{
 echo "<div class=\"alert alert-danger alert-dismissable\">
<button type=\"button\" class=\"close\" data-dismiss=\"alert\" aria-     hidden=\"true\">&times;</button>   

 Some Problem Occurs, Please Try Again. 

</div>";
}
} else {

if ($err1 == 1){
 echo "<div class=\"alert alert-danger alert-dismissable\">
<button type=\"button\" class=\"close\" data-dismiss=\"alert\" aria-   hidden=\"true\">&times;</button> 

  INVALID MOBILE NUMBER!!!

 </div>";
 }      

if ($err2 == 1){
echo "<div class=\"alert alert-danger alert-dismissable\">
 <button type=\"button\" class=\"close\" data-dismiss=\"alert\" aria-    hidden=\"true\">&times;</button>   

YOU DONT HAVE ENOUGH BALANCE !!!

</div>";
}       

if ($err3 == 1){
  echo "<div class=\"alert alert-danger alert-dismissable\">
  <button type=\"button\" class=\"close\" data-dismiss=\"alert\" aria-      hidden=\"true\">&times;</button>    

  AMOUNT MUST BE GRATER THAN 10 !!!

 </div>";
 }      

 if ($err4 == 1){
  echo "<div class=\"alert alert-danger alert-dismissable\">
 <button type=\"button\" class=\"close\" data-dismiss=\"alert\" aria-   hidden=\"true\">&times;</button>

  WRONG PIN !!!

 </div>";
 }      

  }

  }




  ?>