settings.php

<?php
/**
* Custom General Settings
* .
* Crear variables modificables para ReCaptcha-keysite
* - KeySite : cgs_keysite
* - KeySecret: cgs_keysecret
*/


// Añadir un campo suplementario a la sección General de los Ajustes (Settings) del administrador:
$new_general_setting = new new_general_setting();

class new_general_setting {
        function new_general_setting() {
			add_filter( 'admin_init' , array( &$this , 'register_fields' ) );
            add_filter( 'admin_init' , array( &$this , 'register_fields2' ) );
        }
        function register_fields() {
                register_setting( 'general', 'cgs_keysite', 'esc_attr' );
                add_settings_field('cgs_keysite', '<label for="cgs_keysite">ReCaptcha-keysite</label>' , array(&$this, 'fields_html') , 'general' );
        }
        function fields_html() {
                $value = get_option( 'cgs_keysite', '' );
                echo '<input type="text" id="cgs_keysite" name="cgs_keysite" value="' . $value . '" />';
        }

		function register_fields2() {
                register_setting( 'general', 'cgs_keysecret', 'esc_attr' );
                add_settings_field('cgs_keysecret', '<label for="cgs_keysecret">ReCaptcha-keysecret</label>' , array(&$this, 'fields_html2') , 'general' );
        }
        function fields_html2() {
                $value = get_option( 'cgs_keysecret', '' );
                echo '<input type="text" id="cgs_keysecret" name="cgs_keysecret" value="' . $value . '" />';
        }
}