question on header() function

[JRough]

What is the purpose of caching in the header below? I used
something like this for downloading a detail page to Excel but in this
example it looks like it is for cache control? Why would you expire a
header? So the user couldn't send a request after too long of a period
for example in the downloaded excel page?
<?php
header("Expires : Mon, 26 Jul 1997 05:00:00 GMT"); // Date in the
past
header("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT");
// always
modified
header("Cache-Control: no-store, no-cache, must-revalidate"); // HTTP/
1.1
header("Cache-Control: post-check=0, pre-check=0", false);
header("Pragma: no-cache"); // HTTP/1.0
?>

Also, what is the status header for or rather how does it work? You
can get some status information from the server? Is this sent in
conjunction with a header request? What is not found the page or the
server?

header(“Status: 404 Not Found”);

thanks,

[703designs]

On Nov 10, 10:47*pm, JRough <jlro...@yahoo. comwrote:

What is the purpose of caching in the header below? * *I used
something like this for downloading a detail page to Excel but in this
example it looks like it is for cache control? *Why would you expire a
header? So the user couldn't send a request after too long of a period
for example in the downloaded excel page?

<?php
header("Expires : Mon, 26 Jul 1997 05:00:00 GMT"); * *// Date in the
past
header("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT");
* * * * * * * * * * * * * * * * * * * * * * * * * * *// always
modified
header("Cache-Control: no-store, no-cache, must-revalidate"); *// HTTP/
1.1
header("Cache-Control: post-check=0, pre-check=0", false);
header("Pragma: no-cache"); * * * * * * * * * * * * *// HTTP/1.0
?>

Also, what is the status header for or rather how does it work? *You
can get some status information from the server? *Is this sent in
conjunction with a header request? *What is not found the page or the
server?

header(“Status: *404 Not Found”);

thanks,

Take this with a small grain of salt; I'm not an HTTP expert.

I'd expect that you'd use a far-past Expires header to ensure that the
browser downloads the most recent resources. As for the 404, that
means the resource is not found on the server. If the server were not
found, you couldn't connect to the site.

Thomas

[JRough]

On Nov 10, 8:12*pm, 703designs <thomasmal...@g mail.comwrote:

On Nov 10, 10:47*pm, JRough <jlro...@yahoo. comwrote:

What is the purpose of caching in the header below? * *I used
something like this for downloading a detail page to Excel but in this
example it looks like it is for cache control? *Why would you expire a
header? So the user couldn't send a request after too long of a period
for example in the downloaded excel page?

<?php
header("Expires : Mon, 26 Jul 1997 05:00:00 GMT"); * *// Date in the
past
header("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT");
* * * * * * * * * * * * * * * * * ** * * * * * * * *// always
modified
header("Cache-Control: no-store, no-cache, must-revalidate"); *// HTTP/
1.1
header("Cache-Control: post-check=0, pre-check=0", false);
header("Pragma: no-cache"); * * * * * * * * * * ** *// HTTP/1.0
?>

Also, what is the status header for or rather how does it work? *You
can get some status information from the server? *Is this sent in
conjunction with a header request? *What is not found the page or the
server?

header(“Status: *404 Not Found”);

thanks,

Take this with a small grain of salt; I'm not an HTTP expert.

I'd expect that you'd use a far-past Expires header to ensure that the
browser downloads the most recent resources. As for the 404, that
means the resource is not found on the server. If the server were not
found, you couldn't connect to the site.

Thomas

but I don't understand when you use the status header. Do you use it
before you use a header location call? Also what is the boolean
replace in the header for? I'm just trying
to understand the in's and out's of header() function. What do you
use the caching for are there other instances than for downloading as
a pdf or excel content type?

[703designs]

You use caching to make pages load faster and to lighten the server
load. On the user end, a cached page loads nearly instantly (the HTML
and other resources are already on the user's computer). You can cache
your pages on the server side too. Let's say I have a very complex
script that returns 100 user records and all sorts of other mumbo-
jumbo. That page may take a while to build, but if it's cached, it
doesn't need to be built (the generated page is ready on the server).
The drawback is that you will not see any changes made to the page
after the cache is built (until it's rebuilt).

Status codes are very important in HTTP: http://en.wikipedia.org/wiki/List_of_HTTP_status_codes

404 is "not found." 200 is "found." And there are many others
(permanently relocated, temporarily relocated, etc.).

I'm not sure what you mean by "boolean replace."

Thomas

On Nov 10, 11:15*pm, JRough <jlro...@yahoo. comwrote:

On Nov 10, 8:12*pm, 703designs <thomasmal...@g mail.comwrote:

On Nov 10, 10:47*pm, JRough <jlro...@yahoo. comwrote:

What is the purpose of caching in the header below? * *I used
something like this for downloading a detail page to Excel but in this
example it looks like it is for cache control? *Why would you expire a
header? So the user couldn't send a request after too long of a period
for example in the downloaded excel page?

<?php
header("Expires : Mon, 26 Jul 1997 05:00:00 GMT"); * *// Date in the
past
header("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT");
* * * * * * * * * * * * * * * * * * * * * * * * * * *// always
modified
header("Cache-Control: no-store, no-cache, must-revalidate"); *// HTTP/
1.1
header("Cache-Control: post-check=0, pre-check=0", false);
header("Pragma: no-cache"); * * * * * * * * * * * * *// HTTP/1.0
?>

Also, what is the status header for or rather how does it work? *You
can get some status information from the server? *Is this sent in
conjunction with a header request? *What is not found the page or the
server?

header(“Status: *404 Not Found”);

thanks,

Take this with a small grain of salt; I'm not an HTTP expert.

I'd expect that you'd use a far-past Expires header to ensure that the
browser downloads the most recent resources. As for the 404, that
means the resource is not found on the server. If the server were not
found, you couldn't connect to the site.

Thomas

but I don't understand when you use the status header. *Do you use it
before you use a header location call? *Also what is the boolean
replace in the header for? *I'm just trying
to understand the in's and out's of header() function. *What do you
use the caching for are there other instances than for downloading as
a pdf or excel content type?

[Gordon Burditt]

>What is the purpose of caching in the header below? I used

>something like this for downloading a detail page to Excel but in this
example it looks like it is for cache control? Why would you expire a
header? So the user couldn't send a request after too long of a period
for example in the downloaded excel page?

Generally, headers like this encourage a browser to get UP-TO-DATE
dynamic content from the server, as distinguished from old data in
its cache.

><?php
header("Expire s: Mon, 26 Jul 1997 05:00:00 GMT"); // Date in the
past
header("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT");
// always
modified
header("Cach e-Control: no-store, no-cache, must-revalidate"); // HTTP/
1.1
header("Cach e-Control: post-check=0, pre-check=0", false);
header("Pragma : no-cache"); // HTTP/1.0
?>

Also, what is the status header for or rather how does it work? You
can get some status information from the server?

Yes. There are several types of errors that can be returned (page
not found, page moved temporarily, page moved permanently, access
denied, page found OK, etc.) Certain status codes encourage the
browser to try again with a different URL, or to ask the user for
authentication information and resubmit the request.

>Is this sent in
conjunction with a header request? What is not found the page or the
server?

This header is being sent FROM THE SERVER. Do you think it is
likely that the server will send an error code that the server
wasn't found?

>header(“Status : 404 Not Found”);

[Jerry Stuckle]

JRough wrote:

On Nov 10, 8:12 pm, 703designs <thomasmal...@g mail.comwrote:

>On Nov 10, 10:47 pm, JRough <jlro...@yahoo. comwrote:

>>What is the purpose of caching in the header below? I used
something like this for downloading a detail page to Excel but in this
example it looks like it is for cache control? Why would you expire a
header? So the user couldn't send a request after too long of a period
for example in the downloaded excel page?
<?php
header("Expir es: Mon, 26 Jul 1997 05:00:00 GMT"); // Date in the
past
header("Las t-Modified: " . gmdate("D, d M Y H:i:s") . " GMT");
// always
modified
header("Cac he-Control: no-store, no-cache, must-revalidate"); // HTTP/
1.1
header("Cac he-Control: post-check=0, pre-check=0", false);
header("Pragm a: no-cache"); // HTTP/1.0
?>
Also, what is the status header for or rather how does it work? You
can get some status information from the server? Is this sent in
conjunction with a header request? What is not found the page or the
server?
header(“Statu s: 404 Not Found”);
thanks,

Take this with a small grain of salt; I'm not an HTTP expert.

I'd expect that you'd use a far-past Expires header to ensure that the
browser downloads the most recent resources. As for the 404, that
means the resource is not found on the server. If the server were not
found, you couldn't connect to the site.

Thomas

but I don't understand when you use the status header. Do you use it
before you use a header location call? Also what is the boolean
replace in the header for? I'm just trying
to understand the in's and out's of header() function. What do you
use the caching for are there other instances than for downloading as
a pdf or excel content type?

Every HTTP request sends a status. 200 is normal; 404 is Not Found.
There are a bunch of them, each with its own purpose. To get a list of
the valid status codes, google for

HTTP Status.

--
=============== ===
Remove the "x" from my email address
Jerry Stuckle
JDS Computer Training Corp.
js*******@attgl obal.net
=============== ===

[JRough]

On Nov 10, 8:23*pm, gordonb.a5...@b urditt.org (Gordon Burditt) wrote:

What is the purpose of caching in the header below? * *I used
something like this for downloading a detail page to Excel but in this
example it looks like it is for cache control? *Why would you expire a
header? So the user couldn't send a request after too long of a period
for example in the downloaded excel page?

Generally, headers like this encourage a browser to get UP-TO-DATE
dynamic content from the server, as distinguished from old data in
its cache.

<?php
header("Expires : Mon, 26 Jul 1997 05:00:00 GMT"); * *// Date in the
past
header("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT");
* * * * * * * * * * * * * * * * * ** * * * * * * * // always
modified
header("Cache-Control: no-store, no-cache, must-revalidate"); *// HTTP/
1.1
header("Cache-Control: post-check=0, pre-check=0", false);
header("Pragma: no-cache"); * * * * * * * * * * * * *// HTTP/1.0
?>

Also, what is the status header for or rather how does it work? *You
can get some status information from the server? *

Yes. *There are several types of errors that can be returned (page
not found, page moved temporarily, page moved permanently, access
denied, page found OK, etc.) *Certain status codes encourage the
browser to try again with a different URL, or to ask the user for
authentication information and resubmit the request.

Is this sent in
conjunction with a header request? *What is not found the page or the
server?

This header is being sent FROM THE SERVER. *Do you think it is
likely that the server will send an error code that the server
wasn't found?

header(“Status: *404 Not Found”);

thanks, so the cache is in the browser page displayed and if the data
changed it would get more recent data than the expired data on the
page unless you wanted the user to download the same data as what he
originally saw on the page. In any case it is the veriation in the
data at that moment in time viewed by the user and some other later
date in case
he leaves his browser open for awhile then decides to download the
data later.

What is the boolean replace function for in the header function?

thanks

[Jerry Stuckle]

JRough wrote:

On Nov 10, 8:23 pm, gordonb.a5...@b urditt.org (Gordon Burditt) wrote:

>>What is the purpose of caching in the header below? I used
something like this for downloading a detail page to Excel but in this
example it looks like it is for cache control? Why would you expire a
header? So the user couldn't send a request after too long of a period
for example in the downloaded excel page?

Generally, headers like this encourage a browser to get UP-TO-DATE
dynamic content from the server, as distinguished from old data in
its cache.

>><?php
header("Expir es: Mon, 26 Jul 1997 05:00:00 GMT"); // Date in the
past
header("Las t-Modified: " . gmdate("D, d M Y H:i:s") . " GMT");
// always
modified
header("Cac he-Control: no-store, no-cache, must-revalidate"); // HTTP/
1.1
header("Cac he-Control: post-check=0, pre-check=0", false);
header("Pragm a: no-cache"); // HTTP/1.0
?>
Also, what is the status header for or rather how does it work? You
can get some status information from the server?

Yes. There are several types of errors that can be returned (page
not found, page moved temporarily, page moved permanently, access
denied, page found OK, etc.) Certain status codes encourage the
browser to try again with a different URL, or to ask the user for
authenticati on information and resubmit the request.

>>Is this sent in
conjunction with a header request? What is not found the page or the
server?

This header is being sent FROM THE SERVER. Do you think it is
likely that the server will send an error code that the server
wasn't found?

>>header(“Statu s: 404 Not Found”);

thanks, so the cache is in the browser page displayed and if the data
changed it would get more recent data than the expired data on the
page unless you wanted the user to download the same data as what he
originally saw on the page. In any case it is the veriation in the
data at that moment in time viewed by the user and some other later
date in case
he leaves his browser open for awhile then decides to download the
data later.

What is the boolean replace function for in the header function?

thanks

No, the cache is in the browser. The page cannot cache itself.

Also, it doesn't matter if the browser is left open or not. Cache can
also be stored on disk and used even after you reboot.

As to the replace parameter - from the manual:

"The optional replace parameter indicates whether the header should
replace a previous similar header, or add a second header of the same
type. By default it will replace, but if you pass in FALSE as the second
argument you can force multiple headers of the same type. "

--
=============== ===
Remove the "x" from my email address
Jerry Stuckle
JDS Computer Training Corp.
js*******@attgl obal.net
=============== ===

[703designs]

On Nov 11, 6:30*am, Jerry Stuckle <jstuck...@attg lobal.netwrote:

JRough wrote:

On Nov 10, 8:23 pm, gordonb.a5...@b urditt.org (Gordon Burditt) wrote:

>What is the purpose of caching in the header below? * *I used
something like this for downloading a detail page to Excel but in this
example it looks like it is for cache control? *Why would you expire a
header? So the user couldn't send a request after too long of a period
for example in the downloaded excel page?
Generally, headers like this encourage a browser to get UP-TO-DATE
dynamic content from the server, as distinguished from old data in
its cache.

><?php
header("Expire s: Mon, 26 Jul 1997 05:00:00 GMT"); * *// Date in the
past
header("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT");
* * * * * * * * * * * * * * * * * * * * * * * * * * // always
modified
header("Cach e-Control: no-store, no-cache, must-revalidate"); *// HTTP/
1.1
header("Cach e-Control: post-check=0, pre-check=0", false);
header("Pragma : no-cache"); * * * * * * * * * * * * *// HTTP/1.0
?>
Also, what is the status header for or rather how does it work? *You
can get some status information from the server? *
Yes. *There are several types of errors that can be returned (page
not found, page moved temporarily, page moved permanently, access
denied, page found OK, etc.) *Certain status codes encourage the
browser to try again with a different URL, or to ask the user for
authentication information and resubmit the request.

>Is this sent in
conjunction with a header request? *What is not found the page or the
server?
This header is being sent FROM THE SERVER. *Do you think it is
likely that the server will send an error code that the server
wasn't found?

>header(“Status : *404 Not Found”);

thanks, so the cache is in the browser page displayed and if the data
changed it would get more recent data than the expired data on the
page unless you wanted the user to download the same data as what he
originally saw on the page. *In any case it is the veriation in the
data at that moment in time viewed by the user and some other later
date in case
he leaves his browser open for awhile then decides to download the
data later.

What is the boolean replace function for in the header function?

thanks

No, the cache is in the browser. *The page cannot cache itself.

Also, it doesn't matter if the browser is left open or not. *Cache can
also be stored on disk and used even after you reboot.

As to the replace parameter - from the manual:

"The optional replace parameter indicates whether the header should
replace a previous similar header, or add a second header of the same
type. By default it will replace, but if you pass in FALSE as the second
argument you can force multiple headers of the same type. "

--
=============== ===
Remove the "x" from my email address
Jerry Stuckle
JDS Computer Training Corp.
jstuck...@attgl obal.net
=============== ===

Hi JRough,

Keep in mind that caching refers to any method of storing a page for
future use. It can happen on the server or in the browser in the ways
I described earlier. Even more generally, caching refers to storing a
resource or series of resources in advance, usually for performance
reasons.

Just don't want you to take home too narrow of a definition because
you will see the term frequently.

Thanks,
Thomas