functions.php

    /*-----------------------------------------------------
     *   Función de wordpress para administrar las opciones del tema
     *----------------------------------------------------*/

    function theme_settings_page()
    {
    ?>
        <div class="wrap">
        <h1>Theme Panel</h1>
        <form method="post" action="options.php" enctype="multipart/form-data">
            <?php
                settings_fields("section");
                do_settings_sections("theme-options");
                submit_button();
            ?>
        </form>
        </div>
    <?php
    }

    function add_theme_menu_item()
    {
        add_menu_page("Theme Panel", "Theme Panel", "manage_options", "theme-panel", "theme_settings_page", null, 99);
    }

    add_action("admin_menu", "add_theme_menu_item");

    /*-----------------------------------------------------
     *   Función de wordpress para mostrar que opciones
     del tema se van a administrar
     *----------------------------------------------------*/

    function display_search_header()
    {
        ?>
            <input type="checkbox" name="theme_layout" value="1" <?php checked(1, get_option('theme_layout'), true); ?> /> Si
        <?php
    }

    function display_facebook_element()
    {
        ?>
            <input type="text" name="facebook_url" id="facebook_url" value="<?php echo get_option('facebook_url'); ?>" style="width: 50%;" />
        <?php
    }

    function display_twitter_element()
    {
        ?>
            <input type="text" name="twitter_url" id="twitter_url" value="<?php echo get_option('twitter_url'); ?>" style="width: 50%;" />
        <?php
    }

    function display_google_plus_element()
    {
        ?>
            <input type="text" name="google_plus_url" id="google_plus_url" value="<?php echo get_option('google_plus_url'); ?>" style="width: 50%;" />
        <?php
    }

    function display_youtube_element()
    {
        ?>
            <input type="text" name="youtube_url" id="youtube_url" value="<?php echo get_option('youtube_url'); ?>" style="width: 50%;" />
        <?php
    }

    function display_pinterest_element()
    {
        ?>
            <input type="text" name="pinterest_url" id="pinterest_url" value="<?php echo get_option('pinterest_url'); ?>" style="width: 50%;" />
        <?php
    }
    function display_instagram_element()
    {
        ?>
            <input type="text" name="instagram_url" id="instagram_url" value="<?php echo get_option('instagram_url'); ?>" style="width: 50%;" />
        <?php
    }
    function display_linkedin_element()
    {
        ?>
            <input type="text" name="linkedin_url" id="linkedin_url" value="<?php echo get_option('linkedin_url'); ?>" style="width: 50%;" />
        <?php
    }

    function display_phone_whatsapp()
    {
        ?>
            <input type="text" name="phone_ws" id="phone_ws" value="<?php echo get_option('phone_ws'); ?>" style="width: 50%;" />
        <?php
    }
    function display_link_customize()
    {
        ?>
            <input type="text" name="customize_url_ws" id="customize_url_ws" value="<?php echo get_option('customize_url_ws'); ?>" style="width: 50%;" />
        <?php
    }
    function display_email_element()
    {
        ?>
            <input type="text" name="email_url" id="email_url" value="<?php echo get_option('email_url'); ?>" style="width: 50%;" />
        <?php
    }

    /*-----------------------------------------------------
     *   Función de wordpress para administrar los derechos
         de autor y administrar el logo en el pie de pagina
     *----------------------------------------------------*/

    function display_copyright_element()
    {
        ?>
            <input type="text" name="copyright_text" id="copyright_text" value="<?php echo get_option('copyright_text'); ?>" style="width: 50%;" />
        <?php

    }

    function logo_setting()
    {
        $options = get_option('plugin_options');

        if($options=="")
        {
            echo "";
        }
        else
        {
    ?>
        <p><img src="<?php echo $options['logo']; ?>" alt="Logo" /></p>
    <?php
        }
    ?>
        <input type="file" name="logo" />
    <?php
    }

    function display_theme_panel_fields()
    {


        add_settings_field("theme_layout", "Desea desactivar el buscador del header ?", "display_search_header", "theme-options", "section");

        add_settings_field("facebook_url", "Facebook Profile Url", "display_facebook_element", "theme-options", "section");
        add_settings_field("twitter_url", "Twitter Profile Url", "display_twitter_element", "theme-options", "section");
        add_settings_field("google_plus_url", "Google Plus Profile Url", "display_google_plus_element", "theme-options", "section");
        add_settings_field("youtube_url", "Youtube Channel Url", "display_youtube_element", "theme-options", "section");
        add_settings_field("instagram_url", "Instagram Account", "display_instagram_element", "theme-options", "section");
        add_settings_field("pinterest_url", "Pinterest Profile Url", "display_pinterest_element", "theme-options", "section");
        add_settings_field("linkedin_url", "Linkedin Profile Url", "display_linkedin_element", "theme-options", "section");
        add_settings_field("email_url", "E-mail de la empresa", "display_email_element", "theme-options", "section");
        add_settings_field("phone_ws", "Whatsapp number", "display_phone_whatsapp", "theme-options", "section");
        add_settings_field("customize_url_ws", "Enlace de whatsapp", "display_link_customize", "theme-options", "section");

        add_settings_field("copyright_text", "Copyright Text", "display_copyright_element", "theme-options", "section");

        // add settings filed with callback test_logo_display.
        add_settings_field('logo', 'Logo:', 'logo_setting', "theme-options", 'section'); // LOGO

        add_settings_section("section", "Cabecera y Footer Social Media", null, "theme-options");
        register_setting("section", "theme_layout");
        register_setting("section", "facebook_url");
        register_setting("section", "twitter_url");
        register_setting("section", "google_plus_url");
        register_setting("section", "youtube_url");
        register_setting("section", "instagram_url");
        register_setting("section", "pinterest_url");
        register_setting("section", "linkedin_url");
        register_setting("section", "email_url");
        register_setting("section", "phone_ws");
        register_setting("section", "customize_url_ws");
        register_setting("section", "copyright_text");
        register_setting("section", 'logo');
        register_setting('section', 'plugin_options', 'validate_setting');

    }
    add_action("admin_init", "display_theme_panel_fields");

    function validate_setting($plugin_options)
    {
        $keys = array_keys($_FILES);

        $i = 0;
        foreach ( $_FILES as $image )
        {
            // if a files was upload
            if ($image['size'])
            {
                // if it is an image
                if ( preg_match('/(jpg|jpeg|png|gif)$/', $image['type']) ) {
                    $override = array('test_form' => false);
                    // save the file, and store an array, containing its location in $file
                    $file = wp_handle_upload( $image, $override );
                    $plugin_options[$keys[$i]] = $file['url'];
                }
                else
                {
                // Not an image.
                $options = get_option('plugin_options');
                $plugin_options[$keys[$i]] = $options[$logo];
                // Die and let the user know that they made a mistake.
                wp_die('No image was uploaded.');
                }
            }
            // Else, the user didn't upload a file.
            // Retain the image that's already on file.
            else
            {
                $options = get_option('plugin_options');
                $plugin_options[$keys[$i]] = $options[$keys[$i]];
            }

        $i++;

        }

        return $plugin_options;
    }