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Open Source Technologies

Notes the issue altogether. When a server script communicates with a client, it must first send some
headers that provide information about the document to follow. PHP usually handles this for you
automatically, but you can choose to send your own header lines with PHP’s header() function.
To call the header() function, you must be sure that absolutely no output has been sent to the
browser. The first time content is sent to the browser, PHP sends out headers and it’s too late for
you to send your own. Any output from your document, even a line break or a space outside of
your script tags, causes headers to be sent. If you intend to use the header() function in a script,
you must make certain that nothing precedes the PHP code that contains the function call. You
should also check any libraries that you might be using. Listing 9 shows typical headers sent to
the browser by PHP, beginning with line 3, in response to the request in line.
Listing 9 Typical Server Headers Sent from a PHP Script

1. HEAD/listing9.php
2. HTTP/1.0

3. HTTP/1.1 200 OK
4. Date: Sun, 15 Sep 2002 12 : 32 : 28 GMT

5. Server: Apache/2.0.43 (Unix) PHP/4.2.3 mod_ssl/2.8.9 OpenSSL/0.6
6. X-Powered-By: PHP/4.2.3

7. Connection: close
8. Content-Type: text/html

By sending a “Location” header instead of PHP’s default, you can cause the browser to be
redirected to a new page:
header(“Location: http://www.samspublishing.com”);

Assuming that we’ve created a suitably upbeat page called “congrats.html”, we can amend
our number-guessing script to redirect the user if she guesses correctly, as shown in Listing 10.
Listing 10 Using header() to Send Raw Headers

1. <?php
2. $num_to_guess = 42;

3. $num_tries = (isset($_POST[num_tries])) ? $num_tries + 1: 0;
4. $message = “”;

5. if (!isset($_POST[guess])) {
6. $message = “Welcome to the guessing machine!”;

7. } elseif ($_POST[guess] > $num_to_guess) {
8. $message = “$_POST[guess] is too big! Try a smaller number”;

9. } elseif ($_POST[guess] < $num_to_guess) {
10. $message = “$_POST[guess] is too small! Try a larger number”;

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