PHP displays super global variables and display program execution time

<?PHPHeader(' content-type:text/html; Charset=utf-8 ');$t 1=Microtime(true);//record that the script just started to run the timestampEcho"Returns the file name of the current execution script. ".$_server[' Php_self ']. " <br/> "; Echo"Returns the version of the CGI specification used by the server."$_server[' Gateway_interface ']. " <br/> ";Echo"Returns the IP address of the server where the script is currently running. " .$_server[' Server_addr ']. " <br/> ";Echo"Returns the hostname (such as www.baidu.com) of the server where the script is currently running. ".$_server[' server_name ']. " <br/> ";Echo"Returns the server identification string (such as apache/2.2.24). " .$_server[' Server_software ']. " <br/> ";Echo"Returns the name and version of the communication protocol when the page is requested (for example," http/1.0 "). " .$_server[' Server_protocol ']. " <br/> "; Echo"Returns the request method (such as POST) used by the access page. " .$_server[' Request_method ']. " <br/> "; Echo"Returns the timestamp at the start of the request (for example, 1577687494). " .$_server[' Request_time ']. " <br/> "; Echo"Returns the query string, if this page is accessed through a query string. " .$_server[' Query_string ']. " <br/> "; Echo"Returns the request header from the current request. " .$_server[' Http_accept ']. " <br/> ";Echo"Returns the Accept_charset header (for example, utf-8,iso-8859-1) from the current request."$_server[' Http_accept_charset ']. " <br/> ";Echo"Returns the Host header from the current request. " .$_server[' Http_host ']. " <br/> "; Echo"Returns the full URL of the current page (unreliable because it is not supported by all user agents). " .$_server[' Http_referer ']. " <br/> "; Echo"Whether the script is queried through the secure HTTP protocol. " .$_server[' HTTPS ']. " <br/> "; Echo"Returns the IP address of the user who browsed the current page. " .$_server[' REMOTE_ADDR ']. " <br/> "; Echo"Returns the host name of the user who browsed the current page. " .$_server[' Remote_host ']. " <br/> "; Echo"Returns the port number used to connect to the WEB server on the user's machine. " .$_server[' Remote_port ']. " <br/> "; Echo"Returns the absolute path to the current execution script. " .$_server[' Script_filename ']. " <br/> "; Echo"This value indicates the Server_admin parameter in the Apache server configuration file. " .$_server[' Server_admin ']. " <br/> "; Echo"The port used by the WEB server. The default value is "80". " .$_server[' Server_port ']. " <br/> "; Echo"Returns the server version and the virtual host name. ".$_server[' Server_signature ']. " <br/> "; EchoThe base path to the file system (not the document root) where the current script resides. " .$_server[' path_translated ']. " <br/> "; Echo"Returns the path of the current script. " .$_server[' Script_name ']. " <br/> "; Echo"Returns the URI of the current page. " .$_server[' Script_uri ']. " <br/> "; // ... Execute code ...$t 2=Microtime(true);//Log the timestamp when the script ends the runtimeEcho' Time consuming '.round($t 2-$t 1, 3). ' Seconds ';//output time-consuming?>

PHP displays super global variables and display program execution time