如何使用PHP获取XML元素的所有唯一值？

问：

我有一个XML文件。

$xml = simplexml_load_file('example.com');

它看起来像这样：

SimpleXMLElement {#1635 ▼
  +"@attributes": array:1 [▶]
  +"shop": SimpleXMLElement {#1615 ▼
    +"categories": SimpleXMLElement {#1616 ▶}
    +"currencies": SimpleXMLElement {#1617 ▶}
    +"offers": SimpleXMLElement {#1618 ▼
      +"offer": array:1513 [▼
        0 => SimpleXMLElement {#1657 ▶}
        1 => SimpleXMLElement {#1658 ▶}
        2 => SimpleXMLElement {#1659 ▶}
        3 => SimpleXMLElement {#1660 ▶}
        ...
        120158 => SimpleXMLElement {#3169 …10}
      ]
    }
  }
}

我需要报价的所有元素。 通过这种方式，我选择了我需要的元素的路径：

$xml = $xml->shop->offers->offer;

我明白了：

SimpleXMLElement {#995 ▼
  +"@attributes": array:2 [▼
    "id" => "552550582"
    "available" => "true"
  ]
  +"categoryId": "3e71f0c49b"
  +"description": """
    text
    """
  +"modified_time": "1697969563"
  +"name": "Long-sleeve shirt"
  +"param": array:3 [▼
    0 => SimpleXMLElement {#1617 ▶}
    1 => SimpleXMLElement {#1618 ▼
      +"@attributes": array:1 [▼
        "name" => "gender"
      ]
      +"0": "female"
    }
    2 => SimpleXMLElement {#1619 ▼
      +"@attributes": array:1 [▼
        "name" => "color"
      ]
      +"0": "Black"
    }
  ]
  +"picture": array:8 [▶]
  +"price": "6490.0"
  +"url": "example.com ▶"
}

如何从每个选件及其唯一唯一值中获取所有可能的元素。我想看到它是这样的：

$offerValues = [
   'categoryId' = [1,2,3,10...],
   'param@gender' = ['female', 'male'],
   'param@color' = ['black', 'white', 'red'],
   ...
]

我刚刚开始学习 CML，希望得到任何帮助！