"header" call doesn't work before lenghty operation

[a]

Hi everybody,

My config: Win XP (or 2003), Apache 2.0.54, PHP 5.1.2.

I have been trying to handle the case of a lenghty opearation on the server
while providing the user with feedback and ability to cancel, and nothing
seems to work so far.

The following code is one attempt to address this, and it is called as
result of a POST:

//*************st art code*********** ****
session_start;

// prepare exec

// flush session data
session_write_c lose;

// trying to display a "Please wait..." message:
header( "Location: please_wait.php " );

// long exec
exec( ... );

// finally show the result of the exec
header( "Location: exec_result.php " );
//************end code*********** ********

What happens is that only the last header statement has a visual effect, the
first one doesn't do anything, so the user is not presented with the "Please
wait message".

I would appreciate any ideas or code examples on this or the issue of
handling this sort of lengthy operations in general.

Thanks,

A

[Jim Michaels]

"a" <xx*****@pacbel l.net> wrote in message
news:ss******** *********@newss vr27.news.prodi gy.net...

Hi everybody,

My config: Win XP (or 2003), Apache 2.0.54, PHP 5.1.2.

I have been trying to handle the case of a lenghty opearation on the
server while providing the user with feedback and ability to cancel, and
nothing seems to work so far.

The following code is one attempt to address this, and it is called as
result of a POST:

//*************st art code*********** ****
session_start;

// prepare exec

// flush session data
session_write_c lose;

// trying to display a "Please wait..." message:
header( "Location: please_wait.php " );
Location should be followed immediately by exit, at least according to the
documentation. it is supposed to transfer you to a new URL. your long exec
and other header should be in your please wait page, but the header cannot
be, because header() only works at the top of the document before any HTML
is output and before any blank lines (I wouldn't even trust whitespace) are
seen. after all your headers are output, then output a blank line to show
end of headers and then your HTML. sorry. you only get one header() per
page.


// long exec
exec( ... );

// finally show the result of the exec
header( "Location: exec_result.php " );
//************end code*********** ********

What happens is that only the last header statement has a visual effect,
the first one doesn't do anything, so the user is not presented with the
"Please wait message".

I would appreciate any ideas or code examples on this or the issue of
handling this sort of lengthy operations in general.

Thanks,

A

[a]

Thanks for your reply.

Location should be followed immediately by exit, at least according to the
documentation. it is supposed to transfer you to a new URL. your long
exec and other header should be in your please wait page, but the header
cannot be, because header() only works at the top of the document before
any HTML is output and before any blank lines (I wouldn't even trust
whitespace) are seen. after all your headers are output, then output a
blank line to show end of headers and then your HTML. sorry. you only get
one header() per page.

Here is a new attempt, but I still don't see the Please Wait page, instead
it goes straight to the show_result.php

//*********** the form processing.php code*********** *

// long exec (asynchronous - it exits immediately but continues processing),
its end will tested in the next script
exec( ... );

header( "Location: please_wait.php " );

echo( "\nPlease wait" );

flush;
exit;
*********** end of form processing

//********** the "please wait.php" code *************
while( long_operation_ not_done )
usleep( 100000 ); // check the operation each 0.1 secs

header( "Location: show_result.php " );

exit;
//************ end code *************** **

If I put the echo in second php script, I get an error about headers already
sent or similiar.

I don't know php well enough to figure out a solution to unblock me at this
point, so any new idea would be highly appreciated.

A

[Janwillem Borleffs]

a wrote:

Here is a new attempt, but I still don't see the Please Wait page,
instead it goes straight to the show_result.php

You could try something as follows instead:

<?php

if (isset($_GET['pause'])) {
sleep(10);
print 'Done';
exit;
}

print 'Please wait';
header("Refresh : 1;url={$_SERVER['PHP_SELF']}?pause=1");

?>
flush;
exit;

flush();
exit;

(flush() is a function and should be called with parenthesis, while exit is
a language construct where the parenthesis indeed can be omitted).
JW

[Jerry Stuckle]

Janwillem Borleffs wrote:

a wrote:

Here is a new attempt, but I still don't see the Please Wait page,
instead it goes straight to the show_result.php

You could try something as follows instead:

<?php

if (isset($_GET['pause'])) {
sleep(10);
print 'Done';
exit;
}

print 'Please wait';
header("Refresh : 1;url={$_SERVER['PHP_SELF']}?pause=1");

?>

flush;
exit;

flush();
exit;

(flush() is a function and should be called with parenthesis, while exit is
a language construct where the parenthesis indeed can be omitted).
JW

Won't work. You can't send a header call after ANY output.

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[Jerry Stuckle]

a wrote:

Thanks for your reply.

Location should be followed immediately by exit, at least according to the
documentation . it is supposed to transfer you to a new URL. your long
exec and other header should be in your please wait page, but the header
cannot be, because header() only works at the top of the document before
any HTML is output and before any blank lines (I wouldn't even trust
whitespace) are seen. after all your headers are output, then output a
blank line to show end of headers and then your HTML. sorry. you only get
one header() per page.

Here is a new attempt, but I still don't see the Please Wait page, instead
it goes straight to the show_result.php

//*********** the form processing.php code*********** *

// long exec (asynchronous - it exits immediately but continues processing),
its end will tested in the next script
exec( ... );

header( "Location: please_wait.php " );

echo( "\nPlease wait" );

flush;
exit;
*********** end of form processing

//********** the "please wait.php" code *************
while( long_operation_ not_done )
usleep( 100000 ); // check the operation each 0.1 secs

header( "Location: show_result.php " );

exit;
//************ end code *************** **

If I put the echo in second php script, I get an error about headers already
sent or similiar.

I don't know php well enough to figure out a solution to unblock me at this
point, so any new idea would be highly appreciated.

A

I don't think that's going to be very successful, either. You can't
predict what the browser will do as for caching, for instance.

Maybe flash would work?

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Jerry Stuckle
JDS Computer Training Corp.
js*******@attgl obal.net
=============== ===

[Janwillem Borleffs]

Jerry Stuckle wrote:

Won't work. You can't send a header call after ANY output.

Dude, don't judge before trying.
JW

[Jerry Stuckle]

Janwillem Borleffs wrote:

Jerry Stuckle wrote:

Won't work. You can't send a header call after ANY output.

Dude, don't judge before trying.
JW

First of all, I am not your "Dude". And I don't appreciate your
patronizing attitude.

I suggest you learn a few manners. I've probably been doing PHP longer
than you have - and been programming longer than you've been alive.

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

[Janwillem Borleffs]

Jerry Stuckle wrote:

I suggest you learn a few manners. I've probably been doing PHP
longer than you have - and been programming longer than you've been
alive.

You are making assumptions again...
JW

[Jerry Stuckle]

Janwillem Borleffs wrote:

Jerry Stuckle wrote:

I suggest you learn a few manners. I've probably been doing PHP
longer than you have - and been programming longer than you've been
alive.

You are making assumptions again...
JW

I very much doubt it.

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