$_SERVER
$_SERVER is an array containing information such as headers, paths, and script locations. The entries in this array are created by the web server, therefore there is no guarantee that every web server will provide any of these; servers may omit some, or provide others not listed here. However, most of these variables are accounted for in the » CGI/1.1 specification, and are likely to be defined.
Note: When running PHP on the command line most of these entries will not be available or have any meaning.
In addition to the elements listed below, PHP will create additional elements with values from request headers. These entries will be named HTTP_ followed by the header name, capitalized and with underscores instead of hyphens. For example, the Accept-Language header would be available as $_SERVER[‘HTTP_ACCEPT_LANGUAGE’] .
Indices
‘ PHP_SELF ‘ The filename of the currently executing script, relative to the document root. For instance, $_SERVER[‘PHP_SELF’] in a script at the address http://example.com/foo/bar.php would be /foo/bar.php . The __FILE__ constant contains the full path and filename of the current (i.e. included) file. If PHP is running as a command-line processor this variable contains the script name. ‘argv’ Array of arguments passed to the script. When the script is run on the command line, this gives C-style access to the command line parameters. When called via the GET method, this will contain the query string. ‘argc’ Contains the number of command line parameters passed to the script (if run on the command line). ‘ GATEWAY_INTERFACE ‘ What revision of the CGI specification the server is using; e.g. ‘CGI/1.1’ . ‘ SERVER_ADDR ‘ The IP address of the server under which the current script is executing. ‘ SERVER_NAME ‘ The name of the server host under which the current script is executing. If the script is running on a virtual host, this will be the value defined for that virtual host.
Note: Under Apache 2, UseCanonicalName = On and ServerName must be set. Otherwise, this value reflects the hostname supplied by the client, which can be spoofed. It is not safe to rely on this value in security-dependent contexts.
‘ SERVER_SOFTWARE ‘ Server identification string, given in the headers when responding to requests. ‘ SERVER_PROTOCOL ‘ Name and revision of the information protocol via which the page was requested; e.g. ‘HTTP/1.0’ ; ‘ REQUEST_METHOD ‘ Which request method was used to access the page; e.g. ‘GET’ , ‘HEAD’ , ‘POST’ , ‘PUT’ .
Note:
PHP script is terminated after sending headers (it means after producing any output without output buffering) if the request method was HEAD .
‘ REQUEST_TIME ‘ The timestamp of the start of the request. ‘ REQUEST_TIME_FLOAT ‘ The timestamp of the start of the request, with microsecond precision. ‘ QUERY_STRING ‘ The query string, if any, via which the page was accessed. ‘ DOCUMENT_ROOT ‘ The document root directory under which the current script is executing, as defined in the server’s configuration file. ‘ HTTPS ‘ Set to a non-empty value if the script was queried through the HTTPS protocol. ‘ REMOTE_ADDR ‘ The IP address from which the user is viewing the current page. ‘ REMOTE_HOST ‘ The Host name from which the user is viewing the current page. The reverse dns lookup is based on the REMOTE_ADDR of the user.
Note: The web server must be configured to create this variable. For example in Apache HostnameLookups On must be set inside httpd.conf for it to exist. See also gethostbyaddr() .
‘ REMOTE_PORT ‘ The port being used on the user’s machine to communicate with the web server. ‘ REMOTE_USER ‘ The authenticated user. ‘ REDIRECT_REMOTE_USER ‘ The authenticated user if the request is internally redirected. ‘ SCRIPT_FILENAME ‘
The absolute pathname of the currently executing script.
Note:
If a script is executed with the CLI, as a relative path, such as file.php or ../file.php , $_SERVER[‘SCRIPT_FILENAME’] will contain the relative path specified by the user.
‘ SERVER_ADMIN ‘ The value given to the SERVER_ADMIN (for Apache) directive in the web server configuration file. If the script is running on a virtual host, this will be the value defined for that virtual host. ‘ SERVER_PORT ‘ The port on the server machine being used by the web server for communication. For default setups, this will be ’80’ ; using SSL, for instance, will change this to whatever your defined secure HTTP port is.
Note: Under Apache 2, UseCanonicalName = On , as well as UseCanonicalPhysicalPort = On must be set in order to get the physical (real) port, otherwise, this value can be spoofed, and it may or may not return the physical port value. It is not safe to rely on this value in security-dependent contexts.
‘ SERVER_SIGNATURE ‘ String containing the server version and virtual host name which are added to server-generated pages, if enabled. ‘ PATH_TRANSLATED ‘ Filesystem- (not document root-) based path to the current script, after the server has done any virtual-to-real mapping.
Note: Apache 2 users may use AcceptPathInfo = On inside httpd.conf to define PATH_INFO .
‘ SCRIPT_NAME ‘ Contains the current script’s path. This is useful for pages which need to point to themselves. The __FILE__ constant contains the full path and filename of the current (i.e. included) file. ‘ REQUEST_URI ‘ The URI which was given in order to access this page; for instance, ‘ /index.html ‘. ‘ PHP_AUTH_DIGEST ‘ When doing Digest HTTP authentication this variable is set to the ‘Authorization’ header sent by the client (which you should then use to make the appropriate validation). ‘ PHP_AUTH_USER ‘ When doing HTTP authentication this variable is set to the username provided by the user. ‘ PHP_AUTH_PW ‘ When doing HTTP authentication this variable is set to the password provided by the user. ‘ AUTH_TYPE ‘ When doing HTTP authentication this variable is set to the authentication type. ‘ PATH_INFO ‘ Contains any client-provided pathname information trailing the actual script filename but preceding the query string, if available. For instance, if the current script was accessed via the URI http://www.example.com/php/path_info.php/some/stuff?foo=bar , then $_SERVER[‘PATH_INFO’] would contain /some/stuff . ‘ ORIG_PATH_INFO ‘ Original version of ‘ PATH_INFO ‘ before processed by PHP.
Examples
Example #1 $_SERVER example
gethostname
gethostname() gets the standard host name for the local machine.
Parameters
This function has no parameters.
Return Values
Returns a string with the hostname on success, otherwise false is returned.
Examples
Example #1 A simple gethostname() example
See Also
- gethostbyname() — Get the IPv4 address corresponding to a given Internet host name
- gethostbyaddr() — Get the Internet host name corresponding to a given IP address
- php_uname() — Returns information about the operating system PHP is running on
User Contributed Notes 4 notes
Regarding Linux vs. macOS, that is not a difference in OS or PHP. macOS sets the hostname to
Since I built a PHP app that runs on Linux Windows and MacOS I just discovered that using gethostname() behaves differently on different OSes. Linux will return «hostname» while MacOS 10.15 will return «hostname.local» . Have yet to determine how Windows behaves but the difference is worth noting. Only a few days ago I was wanting to get the LAN extension in Linux and was never able to. I was oly hable to get «hostname». In MacOS it is just there. with «hostname.local»
gethostbyname
Returns the IPv4 address of the Internet host specified by hostname .
Parameters
Return Values
Returns the IPv4 address or a string containing the unmodified hostname on failure.
Examples
Example #1 A simple gethostbyname() example
$ip = gethostbyname ( ‘www.example.com’ );
See Also
- gethostbyaddr() — Get the Internet host name corresponding to a given IP address
- gethostbynamel() — Get a list of IPv4 addresses corresponding to a given Internet host name
- inet_pton() — Converts a human readable IP address to its packed in_addr representation
- inet_ntop() — Converts a packed internet address to a human readable representation
User Contributed Notes 31 notes
If you do a gethostbyname() and there is no trailing dot after a domainname that does not resolve, this domainname will ultimately be appended to the server-FQDN by nslookup.
So if you do a lookup for nonexistentdomainname.be your server may return the ip for nonexistentdomainname.be.yourhostname.com, which is the server-ip.
To avoid this behaviour, just add a trailing dot to the domainname; i.e. gethostbyname(‘nonexistentdomainname.be.’)
This function says «Returns the IPv4 address or a string containing the unmodified hostname on failure.
This isn’t entirely true, any hostname with a null byte in it will only return the characters BEFORE the null byte.
$hostname = «foo\0bar» ;
var_dump ( $hostname );
var_dump ( gethostbyname ( $hostname ));
?>
Results:
string ‘foo�bar’ (length=7)
string ‘foo’ (length=3)
Important note: You should avoid its use in production.
DNS Resolution may take from 0.5 to 4 seconds, and during this time your script is NOT being executed.
Your customers may think that the server is slow, but actually it is just waiting for the DNS resolution response.
You can use it, but if you want performance, you should avoid it, or schedule it to some CRON script.
Options for the underlying resolver functions can be supplied by using the RES_OPTIONS environmental variable. (at least under Linux, see man resolv.conf)
Set timeout and retries to 1 to have a maximum execution time of 1 second for the DNS lookup:
putenv ( ‘RES_OPTIONS=retrans:1 retry:1 timeout:1 attempts:1’ );
gethostbyname ( $something );
?>
You should also use fully qualified domain names ending in a dot. This prevents the resolver from walking though all search domains and retrying the domain with the search domain appended.
For doing basic RBL (Real Time Blacklist) lookups with this function do:
$host = ‘64.53.200.156’ ;
$rbl = ‘sbl-xbl.spamhaus.org’ ;
// valid query format is: 156.200.53.64.sbl-xbl.spamhaus.org
$rev = array_reverse ( explode ( ‘.’ , $host ));
$lookup = implode ( ‘.’ , $rev ) . ‘.’ . $rbl ;
if ( $lookup != gethostbyname ( $lookup )) echo «ip: $host is listed in $rbl \n» ;
> else echo «ip: $host NOT listed in $rbl \n» ;
>
?>
Tomas V.V.Cox
gethostbyname and gethostbynamel does not ask for AAAA records. I have written two functions to implement this. gethostbyname6 and gethostbynamel6. I don’t believe this issue has been addressed yet.
They are made to replace gethostbyname[l], in a way that if $try_a is true, if it fails to get AAAA records it will fall back on trying to get A records.
Feel free to correct any errors, I realise that it is asking for *both* A and AAAA records, so this means two DNS calls.. probably would be more efficient if it checked $try_a before making the query, but this works for me so I’ll leave that up to someone else to implement in their own work.. the tip is out there now anyway..
function gethostbyname6($host, $try_a = false) // get AAAA record for $host
// if $try_a is true, if AAAA fails, it tries for A
// the first match found is returned
// otherwise returns false
function gethostbynamel6($host, $try_a = false) // get AAAA records for $host,
// if $try_a is true, if AAAA fails, it tries for A
// results are returned in an array of ips found matching type
// otherwise returns false
$dns6 = dns_get_record($host, DNS_AAAA);
if ($try_a == true) $dns4 = dns_get_record($host, DNS_A);
$dns = array_merge($dns4, $dns6);
>
else < $dns = $dns6; >
$ip6 = array();
$ip4 = array();
foreach ($dns as $record) if ($record[«type»] == «A») $ip4[] = $record[«ip»];
>
if ($record[«type»] == «AAAA») $ip6[] = $record[«ipv6»];
>
>
if (count($ip6) < 1) if ($try_a == true) if (count($ip4) < 1) return false;
>
else return $ip4;
>
>
else return false;
>
>
else return $ip6;
>
>