<?php
class X{
  public $ceff_instance = array();
  protected $filedMethodMappings = NULL;

  public function __construct() {
    $this->ceff_instance = $this->wsMethod_GO();
    $this->filedMethodMappings = $this->ceff_instance;
  }

  protected function wsMethod_GO(){
    return array(1,2,3);
  }
}

$x = new X;
print_r($x->ceff_instance);

Array
(
    [0] => 1
    [1] => 2
    [2] => 3
)