Send Variable Amount a custom payment gateway

Good morning need to send only the value price or amount to this gateway http://newage.systems:81/cm/index.php?cm_monto=$precio get through but I can not llmar to send the url or less amount. Please would help me?

<?php
/**
* WC wcCpg1 Gateway Class.
* Built the wcCpg1 method.
*/
class WC_Custom_Payment_Gateway_1 extends WC_Payment_Gateway {

var $notify_url;

/**
* Constructor for the gateway.
*
* @return void
*/
public function __construct() {
global $woocommerce;

$this->id = ‘wcCpg1’;
$this->icon = apply_filters( ‘woocommerce_wcCpg1_icon’, ” );
$this->has_fields = false;
$this->method_title = __( ‘PASARELA BANCARD’, ‘wcwcCpg1’ );
$this->liveurl = ‘http://newage.systems:81/cm/index.php?cm_monto=$precio&#8217;;
$this->testurl = ”;
$this->method_title = __( ‘PayPal’, ‘woocommerce’ );
$this->notify_url = WC()->api_request_url( ‘WC_Custom_Payment_Gateway_1’ );

// Load the form fields.
$this->init_form_fields();

// Load the settings.
$this->init_settings();

// Define user set variables.
$this->title = $this->settings[‘title’];
$this->description = $this->settings[‘description’];
$this->instructions = $this->get_option( ‘instructions’ );
$this->enable_for_methods = $this->get_option( ‘enable_for_methods’, array() );

// Actions.

if ( version_compare( WOOCOMMERCE_VERSION, ‘2.0.0’, ‘>=’ ) )
add_action( ‘woocommerce_update_options_payment_gateways_’ . $this->id, array( &$this, ‘process_admin_options’ ) );
else
add_action( ‘woocommerce_update_options_payment_gateways’, array( &$this, ‘process_admin_options’ ) );

}

/* Admin Panel Options.*/
function admin_options() {
?>
<h3><?php _e(‘BANCARD’,’wcwcCpg1′); ?></h3>
<table class=”form-table”>
<?php $this->generate_settings_html(); ?>
</table>

<?php
}

/* Initialise Gateway Settings Form Fields. */
public function init_form_fields() {
global $woocommerce;

$shipping_methods = array();

if ( is_admin() )
foreach ( $woocommerce->shipping->load_shipping_methods() as $method ) {
$shipping_methods[ $method->id ] = $method->get_title();
}

$this->form_fields = array(
‘enabled’ => array(
‘title’ => __( ‘Activar/Desactivar’, ‘wcwcCpg1’ ),
‘type’ => ‘checkbox’,
‘label’ => __( ‘Activar Pasarela de Pagos Bancard PARAGUAY’, ‘wcwcCpg1’ ),
‘default’ => ‘no’
),
‘title’ => array(
‘title’ => __( ‘Título’, ‘wcwcCpg1’ ),
‘type’ => ‘text’,
‘description’ => __( ‘This controls the title which the user sees during checkout.’, ‘wcwcCpg1’ ),
‘desc_tip’ => true,
‘default’ => __( ‘Custom Payment Gateways 1’, ‘wcwcCpg1’ )
),
‘description’ => array(
‘title’ => __( ‘Descripción’, ‘wcwcCpg1’ ),
‘type’ => ‘textarea’,
‘description’ => __( ‘This controls the description which the user sees during checkout.’, ‘wcwcCpg1’ ),
‘default’ => __( ‘Desctiptions for Custom Payment Gateways 1.’, ‘wcwcCpg1’ )
),
‘instructions’ => array(
‘title’ => __( ‘Instrucciones’, ‘wcwcCpg1’ ),
‘type’ => ‘textarea’,
‘description’ => __( ‘Instructions that will be added to the thank you page.’, ‘wcwcCpg1’ ),
‘default’ => __( ‘Instructions for Custom Payment Gateways 1.’, ‘wcwcCpg1’ )
),
‘enable_for_methods’ => array(
‘title’ => __( ‘Activar para los siguientes tipos de Envio’, ‘wcwcCpg1’ ),
‘type’ => ‘multiselect’,
‘class’ => ‘chosen_select’,
‘css’ => ‘width: 450px;’,
‘default’ => ”,
‘description’ => __( ‘If wcCpg1 is only available for certain methods, set it up here. Leave blank to enable for all methods.’, ‘wcwcCpg1’ ),
‘options’ => $shipping_methods,
‘desc_tip’ => true,
)
);

}

/* Process the payment and return the result. */
function process_payment ($order_id) {
global $woocommerce;

$order = new WC_Order( $order_id );

// Mark as on-hold
$order->update_status(‘on-hold’, __( ‘Your order wont be shipped until the funds have cleared in our account.’, ‘woocommerce’ ));

// Reduce stock levels
$order->reduce_order_stock();

// Remove cart
$woocommerce->cart->empty_cart();

// Return thankyou redirect
return array(
‘result’ => ‘success’,
‘redirect’ => add_query_arg(‘key’, $order->order_key, add_query_arg(‘order’, $order_id, get_permalink(woocommerce_get_page_id(‘thanks’))))
);
}

/* Output for the order received page. */
function thankyou() {
echo $this->instructions != ” ? wpautop( $this->instructions ) : ”;
}

}

https://wordpress.org/plugins/woocommerce/