Rütimattli_Metabox

class Rm_joboffer_Meta_Box {

	public function __construct() {

		if ( is_admin() ) {
			add_action( 'load-post.php',     array( $this, 'init_metabox' ) );
			add_action( 'load-post-new.php', array( $this, 'init_metabox' ) );
		}

	}

	public function init_metabox() {

		add_action( 'add_meta_boxes',        array( $this, 'add_metabox' )         );
		add_action( 'save_post',             array( $this, 'save_metabox' ), 10, 2 );

	}

	public function add_metabox() {

		add_meta_box(
			'Rm_joboffer_meta_box_shortcode',
			'Shortcode',
			array( $this, 'render_metabox' ),
			'rm_jobofffer',
			'side',
			'high'
		);

	}

	public function render_metabox( $post ) {

		// Retrieve an existing value from the database.
		$rm_joboffer_ = get_post_meta( $post->ID, 'rm_joboffer_', true );

		// Set default values.
		if( empty( $rm_joboffer_ ) ) $rm_joboffer_ = '';

		// Form fields.
		echo '<table class="form-table">';

		echo '	<tr>';
		echo '		<th><label for="rm_joboffer_" class="rm_joboffer__label">' . 'Shortcode' . '</label></th>';
		echo '		<td>';
		echo '			<input type="text" id="rm_joboffer_" name="rm_joboffer_" class="rm_joboffer__field" placeholder="' . '' . '" value="' . esc_attr( $rm_joboffer_ ) . '">';
		echo '		</td>';
		echo '	</tr>';

		echo '</table>';

	}

	public function save_metabox( $post_id, $post ) {

		// Sanitize user input.
		$rm_joboffer_new_ = isset( $_POST[ 'rm_joboffer_' ] ) ? sanitize_text_field( $_POST[ 'rm_joboffer_' ] ) : '';

		// Update the meta field in the database.
		update_post_meta( $post_id, 'rm_joboffer_', $rm_joboffer_new_ );

	}

}

new Rm_joboffer_Meta_Box;