add image to database

<?php
// credentials
$db_user="imageuser";
$db_pass="password";
$db_host="localhost";
$db_name="images";

// check for both fields having content
if ( isset ($_POST['title']) && ($_POST['url']) ){
    // assign title and url variables
    $title=$_POST['title'];
    $url=$_POST['url'];

// first I define connection string
$mysqli= mysqli_connect($db_host, $db_user, $db_pass, $db_name);
$sql_insert = "INSERT INTO urls (id, title, url) VALUES (NULL, '$title', '$url')";

// now make a connection
if($mysqli->connect_errno){
    // if there is a connection error, print the error
    printf("Connect failed: %s\n", $mysqli->connect_error);
    } else {
        // insert image into database:
        if (mysqli_query($mysqli, $sql_insert)) {
            echo "image stored successfully";
        } else {
            printf("Error message: %s\n", mysqli_error($mysqli));
        }
    }
}
?>


<form action="" method="post">
<label for="">title</label>
<input type="text" name="title">
<label for="">URL</label>
<input type="text" name="url">
<input type="submit" value="submit">
</form>