Add custom fields under wp general settings

To add custom fields under wordpress general settings without hacking core code use this as example. Of course you can make it better and write some fancy class for doing this.

add_filter('admin_init', 'my_general_settings_register_fields');

function my_general_settings_register_fields()
{
	register_setting('general', 'my_field', 'esc_attr');
	add_settings_field('my_field', '<label for="my_field">'.__('My Field' , 'my_field' ).'</label>' , 'my_general_settings_fields_html', 'general');
}

function my_general_settings_fields_html()
{
	$value = get_option( 'my_field', '' );
	echo '<input type="text" id="my_field" name="my_field" value="' . $value . '" />';
}