title: PODIO php API call, get array offset of all item fields value using filter by app ID
body: <p>I'm new in API thing, I'm using PHP CLient of PODIO link <a href="http://podio.github.io/podio-php/fields/" rel="nofollow noreferrer">here</a>, I want to get all fields value of all items.</p>
  
  <p>The code below is not working, but if I used <code>PodioItem::get_basic(item_id)</code>, this work to get item related values but I want to get all fields value of all items so I used filter by app ID, I'm getting an error <code>Undefined property: PodioItemCollection::$fields</code> </p>
  
  <pre><code>&lt;?php 
  
  require_once '/PodioAPI.php';
  
  $client_id = "xxxx";
  $client_secret = "xxxx";
  $app_id = xxxx;
  $app_token = "xxxx";
  
  Podio::setup($client_id, $client_secret);
  Podio::authenticate_with_app($app_id, $app_token);
  
  $item = PodioItem::filter($app_id);
  $field_id = 'dashboard-link-2';
  $collection = $item-&gt;fields[$field_id]-&gt;values;
  
  foreach ($collection as $embed) {
    print "Embed id: ".$embed-&gt;embed_id."&lt;br&gt;";
    print "Embed URL: ".$embed-&gt;original_url."&lt;br&gt;";
  }
  </code></pre>
  
  <p>Here's the full response in 2 items available in APP on JSON format using <code>print $item-&gt;as_json(true)</code>. I want to do <code>for each</code> in all fields and their value on the last part of JSON.</p>
  
  <pre><code>{  
     "item_id":535780740,
     "title":"test",
     "link":"https:\/\/podio.com\/trackzen\/",
     "rights":[  
        "view",
        "comment",
        "rate",
        "add_task",
        "add_file",
        "update",
        "add_conversation",
        "subscribe"
     ],
     "created_on":"2016-12-26 05:58:59",
     "app_item_id_formatted":"2",
     "app_item_id":2,
     "ratings":{  
        "like":{  
           "average":null,
           "counts":{  
              "1":{  
                 "total":0,
                 "users":[  
  
                 ]
              }
           }
        }
     },
     "last_event_on":"2016-12-30 10:47:34",
     "comment_count":3,
     "created_by":{  
        "type":"user",
        "id":3584284,
        "avatar_type":"file",
        "avatar_id":250835059,
        "image":{  
           "hosted_by":"podio",
           "hosted_by_humanized_name":"Podio",
           "external_file_id":null,
           "link_target":"_blank"
        },
        "name":"Marlon"
        "url":"https:\/\/podio.com\/users
        "avatar":250835059
     },
     "created_via":{  
        "id":1,
        "auth_client_id":1,
        "name":"Podio",
        "display":false
     },
     "initial_revision":{  
        "created_on":"2016-12-26 05:58:59",
        "created_by":{  
           "type":"user",
           "id":3584284,
           "avatar_type":"file",
           "avatar_id":250835059,
           "image":{  
              "hosted_by":"podio",
              "hosted_by_humanized_name":"Podio",
              "file_id":250835059,
              "external_file_id":null,
              "link_target":"_blank"
           },
           "name":"Marlon",
           "url":"https:\/\/podio.com\/users\/",
           "avatar":250835059
        },
        "created_via":{  
           "id":1,
           "auth_client_id":1,
           "name":"Podio",
           "display":false
        }
     },
     "current_revision":{  
        "revision":13,
        "created_on":"2016-12-30 10:47:34",
        "created_by":{  
           "type":"user",
           "id":3584284,
           "avatar_type":"file",
           "avatar_id":250835059,
           "image":{  
              "hosted_by":"podio",
              "hosted_by_humanized_name":"Podio",
  
              "external_file_id":null,
              "link_target":"_blank"
           },
           "name":"Marlon",
           "url":"https:\/\/podio.com\/users\",
           "avatar":250835059
        },
        "created_via":{  
           "id":1,
           "auth_client_id":1,
           "name":"Podio",
           "display":false
        }
     },
     "fields":{  
        "title":"test",
        "service":[  
           536114669
        ],
        "dashboard-link-2":[  
           {  
              "embed":156461816,
              "file":null
           }
        ],
        "text":" 
  TEST 
  &lt;\/p&gt;",
        "action":[  
           1
        ],
        "deliverables":[  
           536600856
        ]
     }
  }{  
     "item_id":535312848,
     "title":"Test Dashboard",
     "rights":[  
        "view",
        "comment",
        "rate",
        "add_task",
        "add_file",
        "update",
        "add_conversation",
        "subscribe"
     ],
     "created_on":"2016-12-24 09:25:08",
     "app_item_id_formatted":"1",
     "app_item_id":1,
     "ratings":{  
        "like":{  
           "average":null,
           "counts":{  
              "1":{  
                 "total":0,
                 "users":[  
  
                 ]
              }
           }
        }
     },
     "last_event_on":"2016-12-28 12:37:26",
     "comment_count":23,
     "created_by":{  
        "type":"user",
        "id":3584284,
        "avatar_type":"file",
        "avatar_id":250835059,
        "image":{  
           "hosted_by":"podio",
           "hosted_by_humanized_name":"Podio",,
           "file_id":250835059,
           "external_file_id":null,
           "link_target":"_blank"
        },
        "name":"Marlon",
        "url":"https:\/\/podio.com",
        "avatar":250835059
     },
     "created_via":{  
        "id":1,
        "auth_client_id":1,
        "name":"Podio",
        "display":false
     },
     "initial_revision":{  
        "created_on":"2016-12-24 09:25:08",
        "created_by":{  
           "type":"user",
           "id":3584284,
           "avatar_type":"file",
           "avatar_id":250835059,
           "image":{  
              "hosted_by":"podio",
              "hosted_by_humanized_name":"Podio",
              "external_file_id":null,
              "link_target":"_blank"
           },
           "name":"Marlon",
           "url":"https:\/\/podio.com\/users\/",
           "avatar":250835059
        },
        "created_via":{  
           "id":1,
           "auth_client_id":1,
           "name":"Podio",
           "display":false
        }
     },
     "current_revision":{  
        "revision":6,
        "created_on":"2016-12-28 12:37:26",
        "created_by":{  
           "type":"user",
           "id":3584284,
           "avatar_type":"file",
           "avatar_id":250835059,
           "image":{  
              "hosted_by":"podio",
              "hosted_by_humanized_name":"Podio",
              "thumbnail_link":"https:\/\/d2cmuesa4snpwn.cloudfront.net\/public\/",
              "link":"https:\/\/d2cmuesa4snpwn.cloudfront.net\/public\/",
              "file_id":250835059,
              "external_file_id":null,
              "link_target":"_blank"
           },
           "name":"Marlon",
           "url":"https:\/\/podio.com\/users\/",
           "avatar":250835059
        },
        "created_via":{  
           "id":1,
           "auth_client_id":1,
           "name":"Podio",
           "display":false
        }
     },
     "fields":{  
        "title":"Test Dashboard",
        "service":[  
           535311650,
           536114669
        ],
        "dashboard-link-2":[  
           {  
              "embed":155910622,
              "file":null
           }
        ],
        "action":[  
           1
        ],
        "deliverables":[  
           535312645,
           535312468,
           535312239,
           535312097,
           535311935,
           536114763,
           536114718
        ]
     }
  }
  </code></pre>