Jquery自动完成源PHP功能

I would like to attach a php function as a source for my autocomplete functionality, The problem is I am not getting any results back.

PHP function

function getUser(){
    $users = R::findAll('users');
        foreach ($users as $user) {
        echo '<option value="'. $user->name .'" ';
        if($_POST['filterUser'] == $user->name){
            echo "selected";
            }
        echo  $user->name . '</option>';
        }   
    }

Auto completion

$( "#enterUser" ).autocomplete({
      source:'test.php?str=' + $('filterUser').val(),
      messages: 
        { 
            noResults: '', 
            results: function() {} 
        }, 
        select: function( event, ui ) 
        { 
            var selectedObj = ui.item; 
        },
        autoFocus: true
    });
  }); 

In the autocomplete declaration, your source property must be the name of your php file (with some parameters).

Example:

source: 'your_php_file.php?str=' + $('filterUser').val()

In the PHP you must call the function you want to reach, and be sure that it echoes the appropriate JSON string.