Fatal error: Uncaught PDOException: SQLSTATE[23000]: Integrity constraint violation: 1048 Column 'sender' cannot be null in C:\xampp\htdocs\chileanblox.site\include\addfriend.php:23 Stack trace: #0 C:\xampp\htdocs\chileanblox.site\include\addfriend.php(23): PDOStatement->execute(Array) #1 {main} thrown in C:\xampp\htdocs\chileanblox.site\include\addfriend.php on line 23