if i write code php same:
<?php
$title = strip_tags($_POST['title']);
?>
unknown error show!
Notice: Undefined index: title in C:\xampp\htdocs\file.php on line 3
if i write code php same:
<?php
$title = strip_tags($_POST['title']);
?>
unknown error show!
Notice: Undefined index: title in C:\xampp\htdocs\file.php on line 3
 
    
    $_POST has value, after submitting form, so before that anybody can't use $_POST ..
   <?php
         if(isset($_POST['title'])){  
//Here in condition if(array_key_exists ( 'title' , $_POST )) can also be checked... 
//OR if(!empty($_POST)) OR if(!empty($_POST['title'])) can also be put..
            $title = strip_tags($_POST['title']);
         }
        ?>
 
    
    If both form and action in the same page, the first load will show error as there is no data posted. So first checj whether a POST has been made and then assign. Try this
$title = "";
if(isset($_POST['title'])){
    $title = strip_tags($_POST['title']);
}
