if else statements showing error

I want check errors if everything okay.

But it showing all the time errors.

If I dont write into Delivery address then showing only one error.

if I write into Delivery address then it redirects. (So there is no errors but it displays 3 errors (it doesnt show empty cart error only then displays empty cart error when cart is empty so this error checking work but others not))

Error image

Code image

if($_POST && !isset($_GET['invid'])){

$daddr = $_POST["daddr"];
$contactnum = $_POST["contactnum"];
$cost = $_POST["cost"];

$error1=0;
$error2=0;
$error3=0;
$error4=0;

if($daddr == "")
      {
$error1=1;
}

if($cost =="")
      {
$error2=1;
}

if($contactnum =="")
      {
$error3=1;
}

$cou = $pdo->query("SELECT COUNT(*) AS sa FROM carrrt WHERE code='".$unique."'")->fetch();

if($cou['sa']==0)
      {
$error4=1;
}
//------------------------------->> CONDITIONS

$error = $error1+$error2+$error3+$error4;


if ($error == 0){

$dd = date("Ymd", $tm);
$co = $pdo->query("SELECT COUNT(*) AS sa1 FROM orrdr")->fetch();
$onm = $co['sa1']+1; 

$invid="$dd$onm";


$res = $pdo->query("INSERT INTO orrdr SET invid='".$invid."', usid='".$uid."', daddr='".$daddr."', contactnum='".$contactnum."', code='".$unique."', tm='".$tm."', pst='0', dst='0', cost='".$cost."'");
if($res){

echo "<div class=\"alert alert-success alert-dismissable\">W
<button type=\"button\" class=\"close\" data-dismiss=\"alert\" aria-hidden=\"true\">&times;</button>  
Order done! 
</div>";

$pdo->query("UPDATE carrrt SET ordered='1' WHERE code='".$unique."'");
unset($_SESSION["unique"]);
echo "<meta http-equiv=\"refresh\" content=\"2; url=$baseurl/checkout?invid=$invid\" />";

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

if ($error1 == 1){
echo "<div class=\"alert alert-danger alert-dismissable\">
<button type=\"button\" class=\"close\" data-dismiss=\"alert\" aria-hidden=\"true\">&times;</button>    

Delivery address cant be empty!

</div>";
}   

if ($error2 == 1){
echo "<div class=\"alert alert-danger alert-dismissable\">
<button type=\"button\" class=\"close\" data-dismiss=\"alert\" aria-hidden=\"true\">&times;</button>  

Total cost cant be empty 0!

</div>";
}

 if ($error3 == 1){
echo "<div class=\"alert alert-danger alert-dismissable\">
<button type=\"button\" class=\"close\" data-dismiss=\"alert\" aria-hidden=\"true\">&times;</button>  

Contact number cant be empty!
</div>";
}   

 if ($error4 == 1){
echo "<div class=\"alert alert-danger alert-dismissable\">
<button type=\"button\" class=\"close\" data-dismiss=\"alert\" aria-hidden=\"true\">&times;</button>  

cart cant be empty!

</div>";
}   

}

}