默认值未设置NULL

I am having a problem with contenteditable. I am trying to make a ajax post methot using contenteditable. I have two contenteditable div.

If it does not write anything, it must be NULL from the database table but it shows empty post not setting NULL.

AJAX

$("body").on("click", ".post", function() {
   var text1 = $("#text1").html();
   var text2 = $("#text2").html();

   var data = 'text1=' + encodeURIComponent(text1) + '&text2=' + encodeURIComponent(text2);

      $.ajax({
         type: 'POST',
         url: '/requests/post.php',
         data: data,
         cache: false,
         beforeSend: function() {
            // Do something
         },
         success: function(html) {
            console.log("post sended");
         }
      });

});

HTML

<div class="abc" id="text1" contenteditable="true" placeholder="Write something1"></div>
<div class="text2" id="text2" contenteditable="true" placeholder="Write something2"></div>

post.php

<?php 
include "../inc/inc.php";
if(isset($_POST['text1'])){
    $text1 = mysqli_real_escape_string($db, $_POST['text1']);
    $text2 = mysqli_real_escape_string($db, $_POST['text2']);
    $data = $POST->POST($uid,$text1, $text2); 
}
?>

and POST function

public function POST($uid,$text1, $text2) {


    $time=time(); // Current post time
    $ip=$_SERVER['REMOTE_ADDR']; // user ip
    $query = mysqli_query($this->db,"SELECT post_id,text1,text2 FROM `posts` WHERE uid_fk='$uid' order by post_id desc limit 1") or die(mysqli_error($this->db));
    $result = mysqli_fetch_array($query, MYSQLI_ASSOC); 
    // Add the insert POST
     $query = mysqli_query($this->db,"INSERT INTO `posts` (text1,text2, uid_fk,time) VALUES ('$text1','$text2','$uid','$time')") or die(mysqli_error($this->db));

}

All code is working fine.But problem is text2. If doesn't write any text it is showing empty result in database. I want to set id default NULL

Wrong way,

It should looks like this

What i am missing here? Anyone can help me in this regard ?

Add a precheck to the logic, because you have to give NULL or not useing the field in the insert to get an real NULL in the table.

// Add the insert POST
 $text2 = $text2?"'$text2'":'NULL';
 $query = mysqli_query($this->db,"INSERT INTO `posts` (text1,text2, uid_fk,time) VALUES ('$text1',$text2,'$uid','$time')") or die(mysqli_error($this->db));

INSERT TEXT vs NON-TEXT

Insert a real NULL

INSERT INTO posts (text1) VALUES (null)

Insert a text with content NULL

INSERT INTO posts (text1) VALUES ('NULL')

Insert table default:

INSERT INTO posts (text1) VALUES (default)

Insert a text with content default

INSERT INTO posts (text1) VALUES ('default')

To understand it more here an example sql:

INSERT INTO test (testfield) VALUES (null), ('null'), (default), ('') ;

Make a table test with one field VARCHAR(50) NULL DEFAULT NULL and execute the SQL and look what you get. You will get 2 entries with real null, one with empty string and one with an string null.

The problem is you're passing an empty value instead of null itself

Just check if the string is empty and put null if it's empty

if(isset($_POST['text1'])){
    $text1 = mysqli_real_escape_string($db, $_POST['text1']);
    $text2 = mysqli_real_escape_string($db, $_POST['text2']);
    $text1 = !empty($text1) ? $text1 : null;
    $text2 = !empty($text2) ? $text2 : null;
    $data = $POST->POST($uid,$text1, $text2); 
}

And also you're insert statement is adding ' around the string which will make null as string 'null' :

So to process accordingly use pdo:

$dbh = new PDO("mysql:host=$dbhost;dbname=$dbname","$dbusername","$dbpassword");
$stmt = $dbh->prepare("INSERT INTO `posts` (text1,text2, uid_fk,time) VALUES (:text1,:text2,:uid,:time)");

$statement->execute(array(':text1'=>$text1,
                          ':text2', $text2,
                          ':uid', $uid,
                          ':time', $time
                    ));

Edit:

For some reasons if you can't or don't want to use PDO. You'd end up hacking in the sql. Something like:

$text2 = !empty($text2) ? "'".$text2."'":null;
$text1 = !empty($text1) ? "'".$text1."'":null;
$query = mysqli_query($this->db,"INSERT INTO `posts` (text1,text2, uid_fk,time) VALUES ($text1,$text2,'$uid','$time')");