Some HTTP Examples

• A utility which shows all data from incoming requests is here: http://www.cs.ucc.ie/j.bowen/cs3314/resources/showRequest.php

• It is defined as follows:

<?php

echo "<strong>SERVER variables:</strong><br>";

foreach ($_SERVER as $name => $value)

{ echo "$name = $value <br>"; }

echo "<strong>GET variables:</strong><br>";

foreach ($_GET as $name => $value)

{ echo "$name = $value <br>"; }

echo "<strong>POST variables:</strong><br>";

foreach ($_POST as $name => $value)

{ echo "$name = $value <br>"; }

echo "<strong>COOKIE variables:</strong><br>";

foreach ($_COOKIE as $name => $value)

{ echo "$name = $value <br>"; }

?>

• A program which delivers a web-page in the user’s preferred language

http://www.cs.ucc.ie/j.bowen/cs3314/resources/multiLingual.php

• It is defined as follows:<?phpfunction answerInEnglish() {?> <h1>Hello</h1> <?php }function answerInFrench() {?> <h1>Bonjour</h1> <?php }function giveDefaultAnswer() {?> <h1>Default greeting</h1> <?php }

$language=$_SERVER['HTTP_ACCEPT_LANGUAGE']; if ($language=='en-ie') { answerInEnglish(); }else if ($language=='fr') { answerInFrench(); }else { giveDefaultAnswer(); }?>

• Consider this page: http://www.cs.ucc.ie/j.bowen/cs3314/resources/poem.html

• It is defined as follows:<?phpfunction answerInEnglish() {?> <h1>Hello</h1> <?php }function answerInFrench() {?> <h1>Bonjour</h1> <?php }function giveDefaultAnswer() {?> <h1>Default greeting</h1> <?php }

$language=$_SERVER['HTTP_ACCEPT_LANGUAGE']; if ($language=='en-ie') { answerInEnglish(); }else if ($language=='fr') { answerInFrench(); }else { giveDefaultAnswer(); }?>

• Consider this web-page http://www.cs.ucc.ie/j.bowen/cs3314/resources/poem.html

• It contains the following:<poem><poet>Wordsworth</poet><verse><line>I wandered lonely as a cloud</line><line>That floats on high o'er vales and hills</line></verse></poem>

• When we try to view this page, we see this, because the tags in the file are not recognized

• Now consider this file, which has a different name but contains exactly the same text:

http://www.cs.ucc.ie/j.bowen/cs3314/resources/poem.xml

• It contains the following:<poem><poet>Wordsworth</poet><verse><line>I wandered lonely as a cloud</line><line>That floats on high o'er vales and hills</line></verse></poem>

• When we try to view this page, we see this, because the tags in the file are treated as XML tags

• See what happens when we use telnet to access the poem.html file

• The response message contains this header line: Content-Type: text/html

• See what happens when we use telnet to access the poem.xml file

• The response message contains this header line: Content-Type: text/xml

• The different behaviour shown by a browser when we view the two files poem.xml and poem.html is caused by these two different headers

• The header Content-Type: text/htmltells the browser to treat the data in the body of the response

message as a HTML file• The header

Content-Type: text/xmltells the browser to treat the data in the body of the response

message as a XML file

• Consider this PHP program which outputs the XML for the poem

http://www.cs.ucc.ie/j.bowen/cs3314/resources/poem1.php

• It contains the following:<?phpecho “<poem>”;echo “<poet>Wordsworth</poet>”;echo “<verse>”;echo “<line>I wandered lonely as a cloud</line>”;echo “<line>That floats on high o'er vales and hills</line>”;echo “</verse>”;echo “</poem>”;?>

• When we try to view this page, we see this, because the tags in the file are not recognized

• Let’s use telnet to try to view the same page• Notice that the response message contains the header

Content-Type: text/html• This is why the browser did not recognize the tags

• Now consider this PHP program which outputs a header before it outputs the XML text for the poem

http://www.cs.ucc.ie/j.bowen/cs3314/resources/poem2.php

• It contains the following:<?phpheader(“Content-Type: text/xml”);echo “<poem>”;echo “<poet>Wordsworth</poet>”;echo “<verse>”;echo “<line>I wandered lonely as a cloud</line>”;echo “<line>That floats on high o'er vales and hills</line>”;echo “</verse>”;echo “</poem>”;?>

• Let’s use telnet to ask for the page created by this new PHP program

• Notice that the response message contains the header Content-Type: text/xml

• This means that a browser should recognize that the tags are XML tags

• When this page in a browser, the browser does indeed recognize that the tags are XML tags