How to upload image in oop

image_upload.php

=============================FONTEND FORM===============================
<form class="form-horizontal" action="" method="post" enctype="multipart/form-data">
<input type="file" name="image" accept="image/*" multiple />
  ===========================BACKEND================================
    if(isset($_POST['save'])){
        $message = $blog->save_image_info($_POST);
    }
   $query_result = $blog->selectAllimageinfo();
  ============================FUNCTION======================================
public function save_image_info() {
        $image_name = $_FILES['image']['name'];
        $directory ='../asset/blog_image/';
        $image_url =$directory.$image_name;
        $image_type = pathinfo($_FILES['image']['name'], PATHINFO_EXTENSION);
        $image_size = $_FILES['image']['size'];
        $check = getimagesize($_FILES['image']['tmp_name']);
        if($check){
            if(file_exists($image_url)){
                die('This file already exist. Please try anotyer one');
            } else {
                if($image_size>5000000){
                    die('File Size too large.');
                } else {
                    if($image_type != 'jpg' && $image_type != 'png'){
                        die('File is not valid. Please use JPG or PNG');
                    } else {
                        move_uploaded_file($_FILES['image']['tmp_name'],$image_url);
                        $sql ="INSERT INTO tbl_image (image) VALUES('$image_url')";
                        mysqli_query($this->connection, $sql);
                        echo 'Image upload successfully';
                    }
                }
            }
        } else {
            die('The file you upload is not an image. Please upload a valid image file !');
        }    
    }

    public function selectAllimageinfo(){
        $sql="SELECT * FROM tbl_image";
        if(mysqli_query($this->connection, $sql)){
            $query_result = mysqli_query($this->connection, $sql);
            return $query_result;
        } else {
            die('Query Problem'. mysqli_error($this->connection));
        }
    }
  
  ============================FRONT END VIEW==================================
  
  <div class="container">
    <div class="row">
        <?php while ($image_info = mysqli_fetch_assoc($query_result)) { ?>
        <div class="col-md-3">
            <div class="well">
                <img src="<?php echo $image_info['image']; ?>" class="img-responsive" />
            </div>
        </div>
        <?php } ?>
    </div>
</div>