PHP实现自动识别Restful API的返回内容类型

如题，PHP如何自动识别第三方Restful API的内容，自动渲染成 json、xml、html、serialize、csv、php等数据？

其实这也不难，因为Rest API也是基于http协议的，只要我们按照协议走，就能做到自动化识别 API 的内容，方法如下：

1、API服务端要返回明确的 http Content-Type头信息，如：

Content-Type: application/json; charset=utf-8
Content-Type: application/xml; charset=utf-8
Content-Type: text/html; charset=utf-8

2、PHP端（客户端）接收到上述头信息后，再酌情自动化处理，参考代码如下：

 'xml',
 'text/xml'  => 'xml',
 'application/json' => 'json',
 'text/json'  => 'json',
 'text/csv'  => 'csv',
 'application/csv' => 'csv',
 'application/vnd.php.serialized' => 'serialize'
);

if (strpos($contentType, ';'))
{
 list($contentType) = explode(';', $contentType);
}

$contentType = trim($contentType);

if (array_key_exists($contentType, $autoDetectFormats))
{
 echo '_' . $autoDetectFormats[$contentType]($response);
}

//+++++++++++++++++++++++++++++++++++++++++++++++++++++++
// 常用 格式化 方法
//+++++++++++++++++++++++++++++++++++++++++++++++++++++++


function _xml($string)
{
 return $string ? (array)simplexml_load_string($string, 'SimpleXMLElement', LIBXML_NOCDATA) : array();
}


function _csv($string)
{
 $data = array();

 $rows = explode("n", trim($string));
 $headings = explode(',', array_shift($rows));
 foreach( $rows as $row )
 {
 // 利用 substr 去掉 开始 与 结尾 的 "
 $data_fields = explode('","', trim(substr($row, 1, -1)));
 if (count($data_fields) === count($headings))
 {
  $data[] = array_combine($headings, $data_fields);
 }
 }

 return $data;
}


function _json($string)
{
 return json_decode(trim($string), true);
}


function _serialize($string)
{
 return unserialize(trim($string));
}


function _php($string)
{
 $string = trim($string);
 $populated = array();
 eval("$populated = "$string";");

 return $populated;
}