如何单独检查数据库中是否存在PHP用户名或电子邮件

Question

Right now my code checks if both the username and email variables exist in the database because they are both unique keys, but how do I make it so I can check each one individually and output different responses?

Such as if the username exists -> "That username already exists." Or if the email exists, but username does not -> "That email already exists."

<?php
  include 'include/connection.php';

  $username = mysqli_real_escape_string($conn, $_REQUEST['username']);
  $password = mysqli_real_escape_string($conn, $_REQUEST['password']);
  $name = mysqli_real_escape_string($conn, $_REQUEST['name']);
  $email = mysqli_real_escape_string($conn, $_REQUEST['email']);

  $sql = "INSERT INTO userdata (username, password, name, email) VALUES ('$username', '$password', '$name', '$email')";

  if (mysqli_query($conn, $sql)) {
    echo "Your account was created successfully, please login to continue.";
    echo '<form action="login.php">
            <input type="submit" name="login" id="login" value="Login" />
          </form>';
  } else {
    echo "That username already exists, please try again.";
    echo '<form action="registration.php">
            <input type="submit" name="register" id="register" value="Register" />
          </form>';
  }
?>

Answer 1

One of the possible way of having a function and write SQL to check for email and username both.

SELECT username, email from userdata where username = ? OR email = ?

And, loop through the resultset and check if email or username exists and return error message accordingly.

Answer 2

Try This

 $checkUserNameSql = "Select Count(username) as username from userdata WHERE username = '".$username."'";

$result=mysql_query($checkUserNameSql);
$data=mysql_fetch_assoc($result);

echo $data['username'];

If you get a count you can apply your check on that.

Answer 3

Used below code. first you need to check username and email then insert the record.

include 'include/connection.php';
$username = mysqli_real_escape_string($conn, $_REQUEST['username']);
  $password = mysqli_real_escape_string($conn, $_REQUEST['password']);
  $name = mysqli_real_escape_string($conn, $_REQUEST['name']);
  $email = mysqli_real_escape_string($conn, $_REQUEST['email']); 

  $checkUser    = 'select  email ,username from userdata where email="'.$email.'" or username = "'.$username.'"';
  $result       = mysqli_query($conn,$checkUser);
  $row          = mysqli_fetch_assoc($result);
  if(!empty($row)){
    if($row['email']==$email){
        echo "That email already exists. Please try again";
    }
    else if($row['username']==$username){
        echo "That username already exists. Please try again";
    }

    echo '<form action="registration.php">
        <input type="submit" name="register" id="register" value="Register" />
      </form>';
  }
  else{

    $sql = "INSERT INTO userdata (username, password, name, email) VALUES ('$username', '$password', '$name', '$email')";
    if (mysqli_query($conn, $sql)) {
    echo "Your account was created successfully, please login to continue.";
    echo '<form action="login.php">
            <input type="submit" name="login" id="login" value="Login" />
          </form>';
     }
  }