如何获取请求页面的头信息

// 请求数据$data ="{\"Name\":\"pdaloginout\",\"value\":\"1\"}";$url = "http://localhost:801/TestPostAndGet/testHeader/getHeader.php";$ch = curl_init($url);curl_setopt($ch,CURLOPT_CUSTOMREQUEST,"POST");curl_setopt($ch,CURLOPT_POSTFIELDS,$data);curl_setopt($ch,CURLOPT_RETURNTRANSFER,true);curl_setopt($ch,CURLOPT_HTTPHEADER, array('Content-Type: application/json','username: 13540152637','token:321321321321321','Content-Length: ' . strlen($data)));$result = curl_exec($ch);

if ($_SERVER ['REQUEST_METHOD'] == 'POST') {	$body = @file_get_contents ( 'php://input' );		$json = urldecode ( $body );	$jsonPkg = json_decode ( $json, true );	$pkgKey = $jsonPkg ['reqName']; // 获取json中的参数		switch ($pkgKey) {		case "test" :			test ( $jsonPkg );			break;	}} else {	echo "{“success”:“false”,“msg”:“参数错误”}";}function test($jsonPkg) {	$headers = array ();	foreach ( $_SERVER as $key => $value ) {		if ('HTTP_' == substr ( $key, 0, 5 )) {			$headers [str_replace ( '_', '-', substr ( $key, 5 ) )] = $value;		}	}		print_r($headers['USERNAME']);	}