oauth-php How to get the authorization parameter in the request header

I use Fiddler to simulate the request, where to take the authorization request header, why do I use the getallheaders () function to get this value?
Even I write a head also get to Ah, why is authorization not get it?

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I use Fiddler to simulate the request, where to take the authorization request header, why do I use the getallheaders () function to get this value?
Even I write a head also get to Ah, why is authorization not get it?

print_r(apache_request_headers());//看值在不在里面

$_server

$_SERVER['HTTP_USER_AGENT']

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