Slider metabox for links

slider-metabox.php

<?php 
/**
 * Generated by the WordPress Meta Box generator
 * at http://jeremyhixon.com/tool/wordpress-meta-box-generator/
 */

function slide_link_get_meta( $value ) {
	global $post;

	$field = get_post_meta( $post->ID, $value, true );
	if ( ! empty( $field ) ) {
		return is_array( $field ) ? stripslashes_deep( $field ) : stripslashes( wp_kses_decode_entities( $field ) );
	} else {
		return false;
	}
}

function slide_link_get_meta_by_id( $value, $slide_id ) {
	global $post;

	$field = get_post_meta( $slide_id, $value, true );
	if ( ! empty( $field ) ) {
		return is_array( $field ) ? stripslashes_deep( $field ) : stripslashes( wp_kses_decode_entities( $field ) );
	} else {
		return false;
	}
}

function slide_link_add_meta_box() {
	add_meta_box(
		'slide_link-slide-link',
		__( 'Slide Link', 'slide_link' ),
		'slide_link_html',
		'rbk_slides',
		'normal',
		'core'
	);
}
add_action( 'add_meta_boxes', 'slide_link_add_meta_box' );

function slide_link_html( $post) {
	wp_nonce_field( '_slide_link_nonce', 'slide_link_nonce' ); ?>

	<p>Link this slide to a page</p>

	<p>
		<label for="slide_link_custom_url"><?php _e( 'Custom Url', 'slide_link' ); ?></label><br>
		<input type="text" name="slide_link_custom_url" id="slide_link_custom_url" value="<?php echo slide_link_get_meta( 'slide_link_custom_url' ); ?>">
	</p>	

	<p>
		<label for="slide_link_in_page_link"><?php _e( 'In Page Link', 'slide_link' ); ?></label><br>

		<select name="slide_link_in_page_link" id="slide_link_in_page_link">
			<option value=""></option>
			<optgroup label="Pages">
				
			<?php

				$id = slide_link_get_meta( 'slide_link_in_page_link' );

				$pages = get_posts(array('post_type'=>'page', 'posts_per_page'=> -1));
	            foreach( $pages as $page ){
	                    if( $page->ID == $id ){
	                        $selected = 'selected';
	                    } else {
	                        $selected = '';
	                    }
	                    echo '<option value="'.$page->ID.'" ' . $selected . '>'.$page->post_title.'</option>';

	                }
			 ?>
			</optgroup>
			<optgroup label="Posts">
				
			<?php

				$id = slide_link_get_meta( 'slide_link_in_page_link' );

				$pages = get_posts(array('post_type'=>'posts', 'posts_per_page'=> -1));
	            foreach( $pages as $page ){
	                    if( $page->ID == $id ){
	                        $selected = 'selected';
	                    } else {
	                        $selected = '';
	                    }
	                    echo '<option value="'.$page->ID.'" ' . $selected . '>'.$page->post_title.'</option>';

	                }
			 ?>
			</optgroup>
		</select>
	</p>
	<p>
		<label for="rbk_slide_button_text"><?php _e( 'Button Text', 'button_text' ); ?></label><br>
		<input type="text" name="rbk_slide_button_text" id="rbk_slide_button_text" value="<?php echo slide_link_get_meta( 'rbk_slide_button_text' ); ?>">
	</p>	


	<?php
}

function slide_link_save( $post_id ) {
	if ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE ) return;
	if ( ! isset( $_POST['slide_link_nonce'] ) || ! wp_verify_nonce( $_POST['slide_link_nonce'], '_slide_link_nonce' ) ) return;
	if ( ! current_user_can( 'edit_post', $post_id ) ) return;

	if ( isset( $_POST['slide_link_custom_url'] ) )
		update_post_meta( $post_id, 'slide_link_custom_url', esc_attr( $_POST['slide_link_custom_url'] ) );
	if ( isset( $_POST['slide_link_in_page_link'] ) )
		update_post_meta( $post_id, 'slide_link_in_page_link', esc_attr( $_POST['slide_link_in_page_link'] ) );
	if ( isset( $_POST['rbk_slide_button_text'] ) )
		update_post_meta( $post_id, 'rbk_slide_button_text', esc_attr( $_POST['rbk_slide_button_text'] ) );
}
add_action( 'save_post', 'slide_link_save' );

/*
	Usage: slide_link_get_meta( 'slide_link_custom_url' )
	Usage: slide_link_get_meta( 'slide_link_in_page_link' )
*/

?>