所需输入字段的PHP错误消息

Question

I am trying to display an error message if a user has not entered a email and not add a column to the table.

The php code sends the email & randomly generated Code to the database and then displays a message, but if their has been not been a email entered I am trying to get a message to ask for an email and not create a column until done so.

I have achieved this before with other data inputing but I am still new to PHP, I have checked for answers but cannot just find the simple fix which I know it is.

Any help or comments would be greatly appreciated, thanks (Y)

PHP:

 <?php
 if(!empty($_POST['email'])) {
 ?>

   <p>Enter an email</p>

 <?php
  }

 if(isset($_POST['send'])){

 $email = mysqli_real_escape_string($conn,$_POST['email']);

$length = 10;
$inviteCode = "";
$characters = "0123456789abcdefghijklmnopqrstuvwxyz";
for ($p = 0; $p < $length; $p++) {
$inviteCode .= $characters[mt_rand(10, strlen($characters))];
 }

$query = mysqli_query($conn, "INSERT INTO `referrals` (`email`, `inviteCode`) 
 VALUES ('$email', '$inviteCode') ");

if($query){
?>
  <p> "Thank you"</p>
<?php 

  }
  else{
?>

   <p>Sorry there must have been a problem</p>

<?php
    die('Error querying database. ' . mysqli_error($conn));
   }
  } // end brace for if(isset($_POST['Login']))
  // end brace for if(isset($_POST['Login']))
?>

I have achieved this before by putting the following at the top;

 if (empty($_POST) === false) {
    $required_fields = array('email');
     foreach($_POST as $key=>$value) {
       if (empty($value) && in_array($key, $required_fields) === true) {
        $errors[] = 'Please Enter All Information';
        break 1;
       }
    }
  }

The html code for the submit and email input tags are below:

    <input type="text" placeholder="Email" name="email" />  
  <input type="submit" value="send" name="send" />

Answer 1

Add if(!empty($_POST['email'])) to the top of your logic, instead of isset($_POST['send']) unless you are doing something else with the post send value later in your logic. isset will be true if there is an empty string.

To understand why please see:

isset() and empty() - what to use

Edit:

<?php
if(!empty($_POST)){
    if(!empty($_POST['email'])){

        $email = mysqli_real_escape_string($conn,$_POST['email']);

        $length = 10;
        $inviteCode = "";
        $characters = "0123456789abcdefghijklmnopqrstuvwxyz";

        for ($p = 0; $p < $length; $p++) {
             $inviteCode .= $characters[mt_rand(10, strlen($characters))];
        }

         $query = mysqli_query($conn, "INSERT INTO `referrals` (`email`, `inviteCode`) VALUES ('$email', '$inviteCode') ");
         //you might want to consider checking more here such as $query == true as it can return other statuses that you may not want
         if($query){
         ?>
             <p> "Thank you"</p>
         <?php 
        }
        else{
        ?>
           <p>Sorry there must have been a problem</p>
        <?php
            die('Error querying database. ' . mysqli_error($conn));
        }
    }
    else {
    ?>
        <p>Enter an email</p>
    <?php
    }
}
?>