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orange sky
Front End Web Development Techdegree Student 4,945 Pointsheader();
Hello,
Can you please explain how
header("Location: contact-thanks.php");
help prevent the browser or server from processing a contac.php form twice and sending a mail twice.
thanks
orange sky
Front End Web Development Techdegree Student 4,945 PointsHello tim221,
Thank you for the detailed response, but I guess what I am still unsure about is when to use header()? I mean why not use an include()? Based on the video lecture, I know that we don't want our contact-process to send another email, so we use header() to redirect to contact-thanks.php.
Well, my 2 questions are: 1) contact-process.php does not have a form with a submit button, so how can it send another email when use the back button?
2) Sorry for asking the same question again, but in contact-process.php why can't we use include('contact-thanks) instead of header('contact-thank.php');
Cheers!
tim221
18,657 Pointsheader("Location: xyz.php") means stop right here, change the browser URL to this new value, load the new file and execute it. Nothing else in the current file will be executed.
include 'xyz.php' means insert the contents of xyz.php right here and execute it, then continue with the next statement in the current file.
In the video referred to, contact.php is loaded and one of two things happens:
If there was no form submitted (GET request) then the IF statement returns false and it's code is not executed, so form is displayed.
If there was a form submitted (POST request) then the IF statement returns true. It's code is executed resulting in an email being sent. Then the header() statement is executed, which means the browser URL changes to
contact-thanks.phpand that page is then displayed. The rest ofcontact.phpis not executed.
If you used include then the contact-thanks.php page would be executed and then the rest of contact.php would also be executed making a bit of a mess!
I recommend experimenting with these commands on your own. Make a new file called 'test.php' which just echoes something. Then include it in one of the existing pages, and then also redirect to it so you can see how it's different.
5 Answers
tim221
18,657 PointsI totally got this post.
Cool! I don't know how the best answer thing works, but thanks!
It would makes sense to me that everything on contact-process.php was being "displayed" and that once we leave contact-process.php and come back to it again, it makes sense to say everything on that page is being "displayed again" on the browser
That's exactly correct. In the context of PHP, 'displayed' is the same as 'processed' or 'executed'. If the code includes sending an email then that would happen each time too.
but processed to the point that it can send another email??????
It can't send an email containing user data if the form wasn't submitted, but the code can still run and it can try to send an email. Without user data there might be warnings, errors, a blank email, or some combination of those things, but in the case of contact-process.php the code will still run. This is of course a problem, but it's solved solved later in the chapter by putting all the form stuff into a single file.
Any clearer?
orange sky
Front End Web Development Techdegree Student 4,945 PointsHello tim221,
Thank you so much. I totally get the if else flow and head() and include(), but where is the button to vote for best answer. I will send staff a mail to see if they can help me place a vote for this post.
As for the other post on pressing a back button that will cause contact-process.php to send an email, uh I don't know.... There is really nothing about that page that needs to be processsed. All I see are variables storing values, a html page at the bottom, and some include(), so I am having a hard time imagining anything getting processed on that page. It would makes sense to me that everything on contact-process.php was being "displayed" and that once we leave contact-process.php and come back to it again, it makes sense to say everything on that page is being "displayed again" on the browser, but processed to the point that it can send another email??????
Honestly, thank you so much for all your help. I totally got this post.
Cheers!!!!!!
orange sky
Front End Web Development Techdegree Student 4,945 PointsHello tim221,
Ok ok, so I should remember that in Php 'process' and 'display' are the same.
And that as long has I have a php file with code that can send an email, I should make sure to divide that file into 2.
The 1st file should contain only the variables and values and header(),or the code to process the mail, and the 2nd file should be the redirected file so that when the user presses the back button, they can only go back and forth between contact.php and contact-thank.php, and never see contact-process.php?
Is that a good way to look at this process?
** I have informed staff about the voting problem on this post
Cheers!!!
tim221
18,657 PointsOk ok, so I should remember that in Php 'process' and 'display' are the same.
Yes that's a good way to think about it at this stage.
And that as long has I have a php file with code that can send an email, I should make sure to divide that file into 2.
That by itself doesn't solve the problem because whether it's one or two files, if the form processing commands can be triggered by a GET request then you will potentially have the problems we have been discussing.
The best idea is to only process the form on a POST request, because POST requests can't be accessed via the back button or directly by typing a URL. This is implemented in the following videos in this course, the final result is a typical single-file approach which works well, I recommend you check it out.
I have informed staff about the voting problem on this post
Thanks!
orange sky
Front End Web Development Techdegree Student 4,945 PointsHello Tim,
I followed with TreeHouse and the votes for this post, and this is what they said:
""Thanks for writing to us. Unfortunately, you cannot vote on answers that are a direct response to a post (see how it's indented to the right, this indicates it was a direct response instead of a new comment within your post) and it's something we're working on fixing for a future update on the forum.
We apologize for the inconvenience.
Best, Rob""
Anway, thanks a lot for your help on this post
tim221
18,657 PointsThanks for letting me know and all the best.
tim221
18,657 Pointstim221
18,657 PointsThat line redirects processing from the current position to the file specified -
contact-thanks.phpThe IF statement in
contact.phpis the mechanism by which the script decides is the form is to be displayed or the incoming data processed:First there is a GET request to
contact.php, triggered by a normal link. The IF statement evaluates to false, so the processing code is skipped The form is displayed and that request is completeUser presses the submit button, triggering a POST request to
contact.phpThe IF statement is true, so the processing code is executed and email is sent
The
header()statement is processed, redirecting execution tocontact-thanks.php. Thecontact-thanks.phppage is processed/displayed and the request is completeDoes that answer your question?