Add Custom Theme Options in WordPress Easily

Code

<?php
// Hook to add a custom theme options page to the WordPress admin menu
add_action('admin_menu', 'wp_dudecom_add_theme_options_page');

function wp_dudecom_add_theme_options_page() {
    add_menu_page(
        'Custom Theme Options', // Page title
        'Theme Options',        // Menu title
        'manage_options',       // Capability
        'wp-dudecom-theme-options', // Menu slug
        'wp_dudecom_theme_options_page', // Callback function
        'dashicons-admin-generic', // Icon
        61 // Position
    );
}

// Callback function to display the theme options page
function wp_dudecom_theme_options_page() {
    ?>
    <div class="wrap">
        <h1>Custom Theme Options</h1>
        <form method="post" action="options.php">
            <?php
            settings_fields('wp_dudecom_theme_options_group');
            do_settings_sections('wp-dudecom-theme-options');
            submit_button();
            ?>
        </form>
    </div>
    <?php
}

// Hook to register settings, sections, and fields
add_action('admin_init', 'wp_dudecom_register_theme_options');

function wp_dudecom_register_theme_options() {
    register_setting('wp_dudecom_theme_options_group', 'wp_dudecom_theme_options', 'wp_dudecom_sanitize_options');

    add_settings_section(
        'wp_dudecom_main_section',
        'Main Settings',
        'wp_dudecom_main_section_callback',
        'wp-dudecom-theme-options'
    );

    add_settings_field(
        'wp_dudecom_text_field',
        'Custom Text Field',
        'wp_dudecom_text_field_callback',
        'wp-dudecom-theme-options',
        'wp_dudecom_main_section'
    );
}

// Callback function for the main section
function wp_dudecom_main_section_callback() {
    echo '<p>Main settings for the theme.</p>';
}

// Callback function for the text field
function wp_dudecom_text_field_callback() {
    $options = get_option('wp_dudecom_theme_options');
    ?>
    <input type="text" name="wp_dudecom_theme_options[wp_dudecom_text_field]" value="<?php echo isset($options['wp_dudecom_text_field']) ? esc_attr($options['wp_dudecom_text_field']) : ''; ?>" />
    <?php
}

// Sanitize options before saving
function wp_dudecom_sanitize_options($input) {
    $sanitized_input = array();
    if (isset($input['wp_dudecom_text_field'])) {
        $sanitized_input['wp_dudecom_text_field'] = sanitize_text_field($input['wp_dudecom_text_field']);
    }
    return $sanitized_input;
}
?>