Summarize how PHP obtains _php instances of current host, domain name, url, path, port, and parameter

Don't say much, we look at the code directly

Gets the domain name or host address
echo $_server[' Http_host ']. <br/> ";
 
Get page address
echo $_server[' php_self ']. " <br/> ";
 
Gets the URL parameter
echo $_server["Query_string"]. " <br/> ";
 
Get user agent
echo $_server[' Http_referer '. " <br/> ";
 
Gets the full URL of
echo ' http://'. $_server[' http_host '].$_server[' Request_uri '];
echo ' http://' $_server[' http_host '].$_server[' php_self '. $_server[' query_string '];
 
Contains the full URL of the port number
echo ' http://'. $_server[' server_name '. $_server["Server_port"].$_server["Request_uri"];
 
Only fetch path
$url = ' http://'. $_server[' server_name '].$_server[' Request_uri '];
echo dirname ($url);

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