caching example question

jeffb1967 · June 19th, 2003, 01:51 PM

Hey there,

I'm going through Beginning PHP4 and on pages 51-52 there is an example on caching that I thought I'd try out. It's giving me some strange warnings (code & output is below) and I was hoping someone here could help me out with what is wrong. Up to now the examples in the book have worked fine. My register_globals = on. Is there a specific line in my .ini file that I need to change in order for the header functions to work? I wonder if the solution is just a matter of suppressing the PHP warning messages?
In this example I set the caching options then echo the current date and time. I am running Windows 2000 and IIS. thanks

<HTML>
<BODY>

<?php
header("Cache-Control: no-cache, must-revalidate");
header("Pragma: no-cache");
header("Expires: Fri, 20 Jun 2003 12:38:00 GMT");
echo "The date today is: ";
echo gmdate("M d Y");
echo " The time is: ";
echo gmdate("h"), ":", gmdate("i"), ":" , gmdate("s"), " ", gmdate("a");
?>
</BODY>
</HTML>

*****OUTPUT*******

Warning: Cannot modify header information - headers already sent by
(output started at c:\inetpub\wwwroot\php\page52.php:4) in c:\inetpub\wwwroot\php\page52.php on line 5

Warning: Cannot modify header information - headers already sent by
(output started at c:\inetpub\wwwroot\php\page52.php:4) in c:\inetpub\wwwroot\php\page52.php on line 6

Warning: Cannot modify header information - headers already sent by
(output started at c:\inetpub\wwwroot\php\page52.php:4) in c:\inetpub\wwwroot\php\page52.php on line 7

The date today is: Jun 19 2003 The time is: 06:13:58 pm

nikolai · June 19th, 2003, 02:06 PM

Your problem is that you *are* sending output to the browser before calling header().

Any text outside of <?php and ?> tags is considered output text. In your case, you're sending your <HTML> and <BODY> tags (with a few newlines) before ever starting to process your PHP script.

Rewrite yours as:

Code:

<?php
// send headers
header("Cache-Control: no-cache, must-revalidate");
header("Pragma: no-cache");
header("Expires: Fri, 20 Jun 2003 12:38:00 GMT");

//  begin HTML output
echo "<html>\n";
echo "<body>\n";

echo "The date today is: ";
echo gmdate("M d Y");
echo " The time is: ";
echo gmdate("h"), ":", gmdate("i"), ":" , gmdate("s"), " ", gmdate("a");

echo "</body>\n";
echo "</html>\n";

?>

Also note that all tag names should be lower case to conform to new standards.

Take care,

Nik
http://www.bigaction.org/

jeffb1967 · June 19th, 2003, 03:17 PM

Thanks for the help, Nik. Works great.

I got confused because all the php scripts in the book begin and end inside the "body" html tags. So I assume that I would use the format you suggest only when I need to turn off caching, or more generally, whenever I need to call header()? Do any other function calls require this adjustment? thanks

jeff:)