Daily Technology news

HTTP authentication traditionally takes the form of .htaccess files scattered around various directories webmasters want to keep private. A typical .htaccess file, combined with a .htpasswd file, contains information about users that are allowed access to a directory and their password. Even though Apache allows you to customise these permissions, the system is far from flexible - hand-editing files each time you add users, or having to group authorised users together by password is a little behind the times. HTTP authentication is mostly just a matter of sending special HTTP headers to your client asking them to provide access codes, and it is straightforward to implement in PHP as long as you have configured PHP to run as an Apache module (see previous issue for our installation guide). Let's look at basic authentication by creating the file auth.php, which should look like this: if (!isset( $_SERVER [ 'PHP_AUTH_USER' ])) { header ( "WWW-Authenticat...

array headers_list ( void ) We already looked at the headers_sent() function, which tells us whether or not HTTP headers have already been sent to the client. This function duplicates that functionality, but, crucially, also returns headers that have yet to be sent, which when you think about it is a bit more useful. As you can see from the prototype, it takes no parameters, and returns an array. That array contains a numerically indexed list of the headers that are ready for sending, which means we can extend our previous example like this: header ( "Expires: Sat, 22 Dec 1979 05:30:00 GMT" ); echo "This is some text for output. " ; if (! headers_sent ( $filename , $linenum )) { // if no headers have been sent, send one // this will not execute, as we sent the Expires header. header ( "Location: www.yoursite.com" ); exit; } else { echo "Headers alr...

string header ( string header_to_send [, bool replace [, int http_response_code ]]) bool headers_sent ( [string &file [, int &line ]]) As well as status codes, there are a variety of special HTTP headers you can send that give you greater control. For example, the "Location" header instructs browsers to request a different URL, the "Content-Type" header tells browsers what kind of content they are about to receive, and the "WWW-Authenticate" header tells browsers that they need to send some authentication information to proceed. Each of these headers is combined with the HTTP status code to form the header of a HTTP response. This is then followed by two carriage return/line feeds, \r\n\r\n, then the actual content. For example, here is what I got when I sent a request to the popular hardware discussion site, tomshardware.com: HTTP/1.1 200 OK Date: Thu, 31 Jul 2003 21:35:46 GMT Server: Apache/1.3.26 (Unix) mod_...

string gethostbyaddr ( string ip_address ) string gethostbyname ( string hostname ) string gethostbynamel ( string hostname ) There are three functions designed to specifically resolve web host information, and these are gethostbyaddr() , gethostbyname() and gethostbynamel() (that is a lower-case L, by the way). All three take one parameter, and the first two complement each other perfectly - gethostbyname() returns the IP address of a server you specify, and gethostbyaddr() returns the domain name of an IP address you specify. Here is an example of their usage: $sdip = gethostbyname ( "slashdot.org" ); $sddomain = gethostbyaddr ( $sdip ); print "IP: $sdip\n" ; print "Domain: $sddomain\n" ; ?> That should output the following: IP: 66.35.250.150 Domain: slashdot.org By default, gethostbyname() returns the first value IP address for a host, but i...

int dns_check_record ( string host [, string type ]) int dns_get_mx ( string hostname , array mxhosts [, array &weight ]) int dns_get_record ( string hostname [, int type [, array &authns , array &addtl ]]) There are three helpful Domain Name System (DNS) functions that allow you to check and retrieve specific information about other servers on the Internet or the local network. These are dns_check_record() , dns_get_mx() , dns_get_record() , and, sadly, all three are not supported on Windows. The first two from that list, dns_check_record() and dns_get_mx() , both work in roughly the same way - the former returns true if it finds a DNS record for the domain you specify in parameter one, and the latter returns true if it finds an MX record for the domain specified in parameter one, and places the full list of MX servers into a second parameter as an array. If you did not know already, the Domain Name System (DNS), is what turns...

OK, so a ROT13 system is not very helpful, so I would not be surprised if you were wondering whether sockets could be made to do anything useful . Well, consider what socket applications you use - what relies on sockets to work? One of the simplest systems is a web server - an application that listens for requests on a given port, and serves up the files that are asked for. Naturally web servers do a lot more than that - they have to receive POST data, handle file uploads, permissions, filters, and lots more, but we're only interested in the most basic task: serving files. Your average HTTP request will look like this: GET /somefile.txt HTTP/1.1 HOST: www.foo.com Out of all that, we can ignore everything but "/somefile.txt" - that is the file we need to serve up. So, our server waits listening for connections and requests, sending out files as appropriate. Each HTTP response needs to take a very specific format because HTTP splits its response into "...

resource socket_create_listen ( int port [, int backlog ]) resource socket_accept ( resource socket ) int socket_write ( resource socket , int length [, int length ]) string socket_read ( resource socket , int length [, int type ]) void socket_close ( resource socket ) We have just covered the basic use of sockets in PHP, and the next step is to move onto the advanced, more flexible sockets that allow you to create more advanced networking scripts with PHP. There are several functions of interest here: socket_create_listen() , socket_accept() , socket_write() , socket_read() , and socket_close() . In order, those functions create and instruct a socket to listen on a given port, receive a client connecting to the socket, write text out to the client, read text sent by the client, and close the socket. The sockets system starts with socket_create_listen() , which takes a port number to listen on as its only parameter. T...