php - Email Verification/Validation - Error -

i think post may appear "off" topic others. it'll great thank if me out this.

i found email verification code on web. somehow, find confusing @ first when began understand , put on code. there's error , don't know how.

problems:

• the email verification code.
• proper syntax/use of code.

code:

  <?php   if(isset($_post['submit']))     {      $a = $_post['username'];      $b = $_post['password'];      $c = $_post['firstname'];      $d = $_post['lastname'];      $e = $_post['month'];      $f = $_post['day'];      $g = $_post['year'];      $h = $_post['contact'];      $i = $_post['email'];      $j = $_post['confirm'];       $code = md5(uniqid(rand()));      include("dbconnect.php");     $query = "select * `users`.`info` `username`='".$a."' , `email_address`='".$i."'";      $queryquery=$con->query($query);      $checker = mysqli_num_rows($queryquery);       if (($a && $b && $c && $d && $h && $i && $j) == "")         {          print "<script type=text/javascript>         alert('all fields required');         </script>";         }     else     {      if ($checker == 0 && $b != $j)          {          print "<script type=text/javascript>            alert('password mismatch');         </script>";           }      else if($checker == 0)         {          //print $a,$b,$c,$d,$e,$f,$g,$h,$i;                              $insertquery="insert `users`.`info` (`username`,`password`,`firstname`,`lastname`,`month`,`day`,`year`,`contact_number`,`email_address`,`confirm_code`) values ('$a','$b','$c','$d','$e','$f','$g','$h','$i','$code')";                             $insertqueryresult=$con->query($insertquery);                              if ($insertqueryresult)                                 {                                     // send e-mail ...                                     $to=$i;                                      // subject                                     $subject="your confirmation link here";                                      //                                     $header="from admins of publisita.com";                                      // message                                     $message="your comfirmation link \r\n";                                     $message.="click on link activate account \r\n";                                     $message.="http://www.gmail.com/confirmation.php?passkey=$code";                                      // send email                                     $sentmail = mail($to,$subject,$message,$header);                                 }                                      // if not found                              else                                  {                                     print "<script type=text/javascript>                                             alert('not found email in our database')                                             </script>";                                 }                              // if email succesfully sent                             if($sentmail)                             {                                 print "<scrpit type=text/javascript>                                         alert('your confirmation link has been sent email address')                                         </script>";                             }                              else                              {                                 print "<script type=text/javascript>                                     alert('cannot send confirmation link e-mail address')                                     </script>";                             }                              }                              print "<script type=text/javascript>                         alert('successfully registered');                         </script>";                          }                          else                             {                             print "<script type=text/javascript>                                     alert('information been used');                                 </script>";                             }                      }                 }            ?> 

it'll great thing if helped me out

this line:

if (($a && $b && $c && $d && $h && $i && $j) == "") 

is not valid syntax. if want make sure these values aren't empty need check them individually (you want use or (||) since 1 has empty show error. current code require of them empty):

if ($a == "" || $b == "" ....) // or if (empty($a) || empty($b) ....) 

or come more concise way this:

$fields = array($a, $b, $c, $d, $h, $i, $j); if (count(array_filter($fields)) !== count($fields)) 

the code above takes of values checked puts them array. calls array_filter() remove values false (an empty string type juggled boolean false). if number of remaining elements doesn't equal starting number of elements 1 or more empty , need show error.

as pointed out @nicolasdefranoux wide open sql injections. make sure close hole before publishing code.