Accessing the properties of an object of an object dynamically in PHP - php

Question

Given that I'm getting different object results depending of the API I query, here are two examples out of 35 I have to implement:
stdClass Object
(
[mid] => 7127.75
[bid] => 7126.6
[ask] => 7128.9
[last_price] => 7128.8
[low] => 7000.0
[high] => 7492.1
[volume] => 53255.4195502
[timestamp] => 1510265647.9803913
)
stdClass Object
(
[Success] => 1
[Message] =>
[Data] => stdClass Object
(
[AskPrice] => 7095
[BidPrice] => 7070
[Low] => 7001
[High] => 7540
[Volume] => 17.38943459
[LastPrice] => 7090
[Change] => -1.02
[Open] => 7163
[Close] => 7090
)
[Error] =>
)
I want to build mapping variable array to access the object easily.
$xmap["a"]["bid"] = "bid";
$xmap["b"]["bid"] = "Data->BidPrice";
Let's assume $content has the first example object, this will work:
print $content->{$xmap["a"]["bid"]}; // the result is 7128.9
As for the second example object, it does not:
print $content->{$xmap["b"]["bid"]}; // the result is PHP Notice: Undefined property: stdClass::$Data->BidPrice in ...
Can this be done or am I stuck with if statements!

Answer 1

First, convert all the objects into assoc. arrays by using json_encode/decode. You'll find this code multiple times here in stackoverflow
$arr = json_decode(json_encode($obj), true);
Second, I recommend a dot-notation for the key-path, plus a tiny function to find the value in a multidimensional array.
Example:
function fromArray($key, $arr) {
$keys = explode('.', $key);
foreach($keys as $k) {
if (!isset($arr[$k]))
return array(); // return empty array
$arr = $arr[$k];
}
return $arr; // can be a scalar value or array
}
$key = 'my.super.array.content';
$array = ['my' => [
'super' => [
'array' =>[
'content'=>4711
]
]
]
];
var_dump($array, fromArray($key, $array));
/*
array(1) {
["my"]=>
array(1) {
["super"]=>
array(1) {
["array"]=>
array(1) {
["content"]=>
int(4711)
}
}
}
}
int(4711)
*/
I found the dot-notation very useful when dealing with complex structures.

Answer 2

You can convert your objects to arrays and build a large mapping array that needs to be maintained and then explode it and loop through it to access the other arrays; or you can try using patterns. I'm thinking Adapter, but maybe another is a better fit. This is using your second object as an example, but just add as many as needed:
class ContentAdapter {
public function __get($name) {
return $this->obj->{$xmap[$name]};
}
}
class ContentAdapter_API_B extends ContentAdapter {
public $xmap = ['bid' => 'BidPrice', 'ask' => 'AskPrice'];
public function __construct($obj) {
$this->obj = $obj->data;
}
}
Now it is consistant regardless of the object since each has an adapter:
$content = new ContentAdapter_API_B($content);
echo $content->bid;
Using your first object you can either create a child as well (ContentAdapter_API_A in case the structure ever changes) or instantiate directly:
$content = new ContentAdapter($content);
echo $content->bid;
Or obviously just use it as is:
echo $content->bid;
An alternate way without inheritance is to use getters:
class ContentAdapter_API_B {
public function __construct($obj) {
$this->obj = $obj->data;
}
public function getBid() { return $this->obj->BidPrice; }
}
So long as the methods are consistent then it will always work:
$content = new ContentAdapter_API_B($content);
echo $content->getBid;