phpunit - How do I stub this function in PHP -

i have following class want test:

<?php  namespace freya\component\pagebuilder\fieldhandler;  use freya\component\pagebuilder\fieldhandler\ifieldhandler;  /**  * used set of non empty, false or null fields.  *  * core purpose use class determine a) advanced custom fields installed  * , b) set of fields child page.  *  * cavete here class requires have child pages have custom fields  * want display on each of pages. getting other page information such content, title, featured image  * , other meta boxes left ot end developer.  *  * @see freya\component\pagebuilder\fieldhandler\ifieldhandler  */ class fieldhandler implements ifieldhandler {      /**      * {@inheritdoc}      *      * @return bool      */     public function checkforafc() {         return function_exists("register_field_group");     }      /**      * {@inheritdoc}      *      * @param $childpageid - id of child page may or may not have custom fields.      * @return mixed - null or array      */     public function getfields($childpageid) {         $fieldsforthispage = get_fields($childpageid);          if (is_array($fieldsforthispage)) {             foreach ($fieldsforthispage $key => $value) {                 if ($value === "" || $value === false || $value === null) {                     unset($fieldsforthispage[$key]);                 }             }              return $fieldsforthispage;         }          return null;     } } 

i can test of 1 thing want stub get_fields() function return type of array used how ever rest of function uses it, in case looping through it.

the part don't know how in php stub function that's being called , return x.

so how stub get_fields?

you can use trick here unqualified function name get_fields(). since don't use fully qualified function name \get_fields() php first try find function in current namespace , fall global function name.

for definition of qualified , unqualified, see: http://php.net/manual/en/language.namespaces.basics.php (it's similar absolute , relative filenames)

so have define function in namespace of class, test case, this:

namespace freya\component\pagebuilder\fieldhandler;  function get_fields() {     return ['x']; }  class fieldhandlertest extends \phpunit_test_case {     ... } 

additional notes:

• you can same core functions, described here: http://www.schmengler-se.de/en/2011/03/php-mocking-built-in-functions-like-time-in-unit-tests/
• this trick works functions, not classes. classes in global namespace must referenced leading backslash.