wordpress image upload

<label for="mv_file"><?php _e('<b>Vorschaubild 1</b> <br><em>(oder leer lassen)</em>', 'mvafsp');?></label>
    <input type="file" name="mv_file" id="mv_file" />
    <div class="mv-clear"></div>
    
    <label for="mv_file"><?php _e('<b>Vorschaubild 2</b> <br><em>(oder leer lassen)</em>', 'mvafsp');?></label>
    <input type="file" name="mv_file" id="mv_file" />
    <div class="mv-clear"></div>
    
    <label for="mv_file"><?php _e('<b>Vorschaubild 3</b> <br><em>(oder leer lassen)</em>', 'mvafsp');?></label>
    <input type="file" name="mv_file" id="mv_file" />
    <div class="mv-clear"></div>

// Check if the type is supported. If not, throw an error.
        if(in_array($uploaded_type, $supported_types)) {
            $mv_file = get_post_meta($post_id, 'mv_file', true);
            if ($mv_file) {
                $mv_file_path = WP_CONTENT_DIR.'/multiverso/'.$mv_file['file'];
                if (file_exists($mv_file_path)) unlink($mv_file_path);
                isset( $_POST['my_image_upload_nonce'], $_POST['post_id'] ) 
                && wp_verify_nonce( $_POST['my_image_upload_nonce'], 'my_image_upload' )
                && current_user_can( 'edit_post', $_POST['post_id'] );
            }
            
            // Use the WordPress API to upload the file
            require_once(ABSPATH . 'wp-admin/includes/admin.php');
            require_once(ABSPATH . 'wp-admin/includes/file.php' );
            require_once(ABSPATH . 'wp-admin/includes/media.php');
            $upload = wp_handle_upload( $_FILES['mv_file'], array( 'test_form' => false ) );
            
            $attachment_id = media_handle_upload( 'my_image_upload', $_POST['post_id'] );
    
            if ( is_wp_error( $attachment_id ) ) {
        // There was an error uploading the image.
        } else {
        // The image was uploaded successfully!
    }

<fieldset>
       <label for="mv_file_images"><?php _e('<b>Vorschaubild 1</b> <br><em>(oder leer lassen)</em>', 'mvafsp');?></label>
    <input type="file" name="my_image_upload" id="my_image_upload"  multiple="false" />
    <input type="hidden" name="post_id" id="post_id" value="55" />
    <?php wp_nonce_field( 'my_image_upload', 'my_image_upload_nonce' ); ?>
    <div class="mv-clear"></div>
   
    <label for="mv_file_images"><?php _e('<b>Vorschaubild 2</b> <br><em>(oder leer lassen)</em>', 'mvafsp');?></label>
    <input type="file" name="my_image_upload" id="my_image_upload"  multiple="false" />
    <input type="hidden" name="post_id" id="post_id" value="55" />
    <?php wp_nonce_field( 'my_image_upload', 'my_image_upload_nonce' ); ?>
    <div class="mv-clear"></div>
    
    <label for="mv_file_images"><?php _e('<b>Vorschaubild 3</b> <br><em>(oder leer lassen)</em>', 'mvafsp');?></label>
    <input type="file" name="my_image_upload" id="my_image_upload"  multiple="false" />
    <input type="hidden" name="post_id" id="post_id" value="55" />
    <?php wp_nonce_field( 'my_image_upload', 'my_image_upload_nonce' ); ?>
    <div class="mv-clear"></div>
    </fieldset>

<?php


// Check that the nonce is valid, and the user can edit this post.
if ( 
    isset( $_POST['my_image_upload_nonce'], $_POST['post_id'] ) 
    && wp_verify_nonce( $_POST['my_image_upload_nonce'], 'my_image_upload' )
    && current_user_can( 'edit_post', $_POST['post_id'] )
) {
    // The nonce was valid and the user has the capabilities, it is safe to continue.


    // These files need to be included as dependencies when on the front end.
    require_once( ABSPATH . 'wp-admin/includes/image.php' );
    require_once( ABSPATH . 'wp-admin/includes/file.php' );
    require_once( ABSPATH . 'wp-admin/includes/media.php' );
    $upload = wp_handle_upload( $_FILES['mv_file'], array( 'test_form' => false ) );
    // Let WordPress handle the upload.
    // Remember, 'my_image_upload' is the name of our file input in our form above.
    $attachment_id = media_handle_upload( 'my_image_upload', $_POST['post_id'] );
    
    if ( is_wp_error( $attachment_id ) ) {
        // There was an error uploading the image.
    } else {
        // The image was uploaded successfully!
    }


} else {


    // The security check failed, maybe show the user an error.
}