HTTP Response Header Lines

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This section describes HTTP response header lines in 3 groups. Commonly used header lines are Date, Cache-Control, Last-Modified, Content-Length, Connection, Content-Type, Expires, Set-Cookie, Server, etc.

HTTP/1.1 response header lines allow the server to passes additional information about the response which cannot be placed in the status line. Header lines can be divided into three groups:

1. General header lines - Information about the transmission of the entire response message:

   Cache-Control      
   Connection         
   Date               
   Pragma             
   Trailer            
   Transfer-Encoding  
   Upgrade            
   Via                
   Warning          

2. Response header lines - Information about the response:

   Accept-Ranges     
   Age               
   ETag              
   Location          
   Proxy-Authenticate
   Retry-After       
   Server            
   Vary              
   WWW-Authenticate

3. Entity header lines - Information about the data requested by the client:

   Allow              
   Content-Encoding   
   Content-Language   
   Content-Length     
   Content-Location   
   Content-MD5        
   Content-Range      
   Content-Type       
   Expires            
   Last-Modified      

As examples, here is a list of all header lines from an HTTP response returned from the Yahoo Web serer:

Date: Sun, 13 Nov 2005 04:34:17 GMT
P3P: policyref="http://info.yahoo.com/w3c/p3p.xml", CP="CAO DSP CO...
Cache-Control: private
Vary: User-Agent
X-XRDS-Location: http://open.login.yahooapis.com/openid20/www.yaho...
Last-Modified: Sun, 13 Nov 2005 04:31:16 GMT
Accept-Ranges: bytes
Content-Length: 9490
Connection: close
Content-Type: text/html; charset=utf-8

Last update: 2005.

Sections in This Chapter

What Is an HTTP Response?

HTTP Response Header Lines

header() - Inserting a Raw Header Lines

HttpRequestGet.php - Viewing Header Lines

Response Header Lines of Static Files

HttpHeaderLines.php - Examples of Inserting Header Lines

Location: - Forcing the Browser to Redirect to Another URL

Content-Type: - Generating Non-HTML Response Body

Content-Disposition: - Sending Files for Downloading