Functional selectable sliders as page meta option, uncommented version - accounts for the Revolution Slider and Smart Slider 3 plugins, trivial to add support for more plugins

sliders-functional-clean.php

<?php 
// content.php
$config = array(
    'title' => __('General Options', 'theme_admin'),
    'group_id' => 'general',
    'context' => 'normal',
    'priority' => 'low',
    'types' => array( 'page' )
);
$options = array(
  array(
        'type' => 'on_off',
        'id' => 'pageslider',
        'toggle' => 'toggle-show-pageslider',
        'title' => __('Show Image Slider', 'theme_admin'),
        'description' => __('Turn on to enable an image slider at the top of the page', 'theme_admin'),
        'default' => 'off',
    ),
    array(
        'type' => 'select',
        'id' => 'pageslider_alias',
        'toggle_group' => 'toggle-show-pageslider toggle-show-pageslider-on',
        'title'         => __('Choose Slider', 'theme_admin'),
        'description'     => __('Select the slider to use', 'theme_admin'),
        'source'        => array(
        'pageslider'    => true
            )
        )
  );
  new metaboxes_tool($config, $options);
?>
<?php
// input-tool.php:
class input_tool {
    var $options;
    var $config;
    var $saved_data;
    var $multi_counter = 0;

    function input_tool( $options, $config ) {
        $this->options = $options;
        $this->config = $config;
    }

    function get_saved_theme_option() {
        $groups = get_option( THEME_SLUG . '_options' );
        if( is_array($groups) ) {
            foreach ( $groups as $group_key => $group ) {
                if( is_array( $group ) ) {
                    foreach ( $group as $field_key => $field ) {
                        $options[ $group_key . '_' . $field_key ] = stripslashes_deep( $field );
                    }
                }
            }
            return $options;
        }
        return false;
    }
    
    function get_saved_meta_option() {
        global $post;
        $keys = @get_post_custom_keys( $post->ID );
        if( is_array($keys) ) {
            foreach ( $keys as $key ) {
                $metas[ preg_replace('/_/', '', $key, 1) ] = get_post_meta( $post->ID, $key, true );
            }
            return $metas;
        }
        return false;
    }
function select( $option ) {
  $value = $this->value($option);
  $toggle = ( isset($option['toggle']) ) ? ' toggle="' . $this->toggle($option) . '"' : '';
  if( isset( $option['source']['pageslider']) ) {
    $meta = get_post_meta( get_the_ID(), 'AMTA_pageslider', true); //in case it is a post/page option
    $meta = get_option('AMTA_pageslider', true); //in case it is a theme option
    require 'pageslider.php';
    $pagesliders = array_merge($revsliders, $smartsliders);
      foreach( $pagesliders as $pageslider ) {
      $source[ $pageslider->title ] = $pageslider->title;
      $checked="";
      if($pageslider->title == $meta) $checked="selected";
      }
  echo '</select>';
        }
    ?>
<?php
// pageslider.php
function get_revsliders($output_type=OBJECT) {
    if( shortcode_exists('rev_slider') ){
        global $wpdb;
        return $wpdb->get_results("SELECT * FROM wp_revslider_sliders", OBJECT);
    }
}
$revsliders = get_revsliders();

function get_smartsliders($output_type=OBJECT) {
    if( shortcode_exists('smartslider3' ) ){
        global $wpdb;
        return $wpdb->get_results("SELECT * FROM wp_nextend2_smartslider3_sliders", $output_type);
    }
}
$smartsliders = get_smartsliders();
?>
<?php
// stack-page_content_home.php
 $pageslider_alias = get_post_meta( get_the_ID(), '_general_pageslider_alias', true ); // _general_slider_alias
?>
<div class="stack-pageslider-container" id="<?php echo $pageslider_alias; ?>">

<div class="pageslider" id="<?php echo $pageslider_alias; ?>" >
<?php
    require THEME_FUNCTIONS_DIR . '/pageslider.php';
    $pageslider_alias = get_post_meta( get_the_ID(), '_general_pageslider_alias', true );
    if(shortcode_exists('rev_slider')) {
        foreach($revsliders as $revslider){
            if(isset($revslider->title) && $revslider->title == $pageslider_alias) {
                putRevSlider("$revslider->alias"); } } }
    if( shortcode_exists('smartslider3' ) ){
        foreach($smartsliders as $smartslider){
            if(isset($smartslider->title) && $smartslider->title == $pageslider_alias) {
                echo do_shortcode('[smartslider3 slider="' . $smartslider->id . '"]');
            } } };
 ?>
 </div>