1. How to check in signup form your email address is already exist in php.......
१ आपका email address already exist  है  या नहीं चेक by php.....

<?php
  if(isset($_POST['submit1'])){
        $email   = $_POST['email1'];
        $sql21="SELECT * FROM `user_register` WHERE `email1`='".$email."'";
        $query21=$mysqli->query($sql21);
        $row21=mysqli_fetch_array($query21);
          if($row21['email1']==$_POST['email1']){
            echo "<script>alert('this user already exist');</script>";
            echo "<script>window.location.href='user_signup.php';</script>";
          }
        else{
     
         $name   = $_POST['name1'];
         $email   = $_POST['email1'];
      $password  = $_POST['password1'];
         $gender = $_POST['gender1'];
            $dob =$_POST['dob1'];
          $select=$_POST['select1'];
           $file =$_FILES['file1'];
      $image_name=$file['name'];//image name
$destination="image/".$image_name;
if(move_uploaded_file($file['tmp_name'] ,$destination)){}

  $cat = "INSERT INTO `user_register` (`name1`,`email1`,`password1`,`gender1`,`dob1`,`select1`,`file1`) VALUES('$name','$email','$password','$gender','$dob','$select','$image_name')";
  $dog=$mysqli->query($cat);


  if($dog){
  echo '<script type="text/javascript">alert("signup successful")</script>';
    echo '<script type="text/javascript">window.location.href="index.php";</script>';
  }
  else
      {
         echo "error";
        }
     }
    }

 ?>