PHP and Javascript

dugawug

Is this possible?
I want to take a PHP variable and have Javascript access it. More specifically, when a page loads, I start off querying the database creating a PHP variable with it. Of course, that all happens server side. The page loads but then I want to allow Javascript to access that PHP variable client side. Is this possible? I can't seem to get it to work.

I read that this should work, a Javascript variable that calls the PHP variable this way:

var JavascriptVariable = <?php echo $phpVariable; ?>;

Piranha

It is not possible that a javascript variable can call a PHP variable since javascript is client side and PHP is server side. However you may be able to make the PHP variable into a javascript variable, and what you use will probably work for numbers. But when it's text strings I just assume that javascript is like every other programming language, you should do it like this:

var JavascriptVariable = "<?php echo $phpVariable; ?>";

anoopmail

one more thing, it won't work if it is in separate .js file rather than .php file because js files are not parsed trough php..

dugawug

ok, well, i'll try it some more, but i'm not sure if i'm clear if it's possible or not :queasy:

let me explain more theoretically what i want to do:

while having users enter data into a web form, i want to immediately alert them if an email they enter already exists in the database. to do this, i was hoping to first query the database, put all the emails in one giant PHP variable string...then somehow write this PHP variable as a javascript variable so the following function can access it...

after a user types an email into the form field, use a javascript event (onBlur) to call a js function that runs a string search checking if the email just entered exists in the hopefully now Javascript variable of all emails....

pipe dream? ideas on a better way to do it?

Piranha

I don't know enough javascript to tell you how to do. But I know enough about data communication and sizes to know that it will not be possible to do it as you want. Let's assume that your site is a big hit and you get 1.000.000 users. With a medium length of 15 characters the server would have to create and send a file that is 30 MB big (assuming that each sign is 2 bytes). So just forget that way of doing it.

Of course there is the possibility to submit the form and then check, but you clearly stated that you don't want it this way. I don't know any other way of doing it. hopefully someone else can help you out.

dugawug

Piranha wrote:
I don't know enough javascript to tell you how to do. But I know enough about data communication and sizes to know that it will not be possible to do it as you want. Let's assume that your site is a big hit and you get 1.000.000 users. With a medium length of 15 characters the server would have to create and send a file that is 30 MB big (assuming that each sign is 2 bytes). So just forget that way of doing it.

well, right now we actually only have 3000 emails. so it's a very manageable string.

Piranha wrote:
Of course there is the possibility to submit the form and then check, but you clearly stated that you don't want it this way. I don't know any other way of doing it. hopefully someone else can help you out.

yeah, a user basically takes the time to fill out a lot of info that is fairly useless if the email already exists. so i was hoping to run a check as soon as the email is entered. it doesn't sound possible though. i see a lot about javascript/php potentially communicating, but maybe in the way i need isn't going to work.

Piranha

dugawug wrote:
well, right now we actually only have 3000 emails. so it's a very manageable string.

Does that mean that you rather do the work many times than just one? Why not design it for the worst (best) case at once?

And remember that all the mail addresses would be available to everyone with your way of doing things. Then there is probably a username, only a password needed to get access to others pages.

dugawug wrote:
yeah, a user basically takes the time to fill out a lot of info that is fairly useless if the email already exists. so i was hoping to run a check as soon as the email is entered. it doesn't sound possible though. i see a lot about javascript/php potentially communicating, but maybe in the way i need isn't going to work.

And there is no way to go back to the form and have the information already set? Like using value="<?php echo $_POST['name'] ?>"? Or to first fill in the email, then continue and get an answer to know if the mail is already there?