I know PHP runs first but is there a way to get PHP to wait on an ajax request and then run its script? I have a php script here that I want to run but I NEED a variable from my JS file in order for it to run successfully. So was wondering if it's possible?
What I have is a normal request in my JS:
var myvar = data;
$.get('phpscript.php', {myvar: myvar} );
And in PHP:
$myphp = $_GET['myvar'];
But if i echo $myphp it returns "undefined", if I alert it however It displays the value; which means the php script is running before it even gets the request from ajax. Any way I could make the PHP wait?
Thanks.
Put the PHP that requires a variable in its own script and call it from the ajax call, once the ajax call gets a response update the DOM as needed.
PHP runs on server, then javascript runs on client to make the ajax call, then PHP runs on server returning data, then the javascript gets the data and does something with it.
$.get('phpscript.php', {myvar: myvar}, function(data) {
$('.result').html(data);
});
Inside the php file have something like:
$myphp = $_GET['myvar'];
echo $myphp;
The short answer is, no, you can't make PHP wait. PHP only runs on the server-side, by the time the AJAX request is sent, by definition, the page is already been sent to the client.
You'll probably have to do some refactoring. If the variable absolutely needs to be used for a PHP function, then you may need to move that logic into 'phpscript.php' or (less optimally) you may need to issue another AJAX request when you get the response from the first.
But my guess is that more commonly, you'll probably just have to figure out how to do what you want with javascript. If all you want is something equivalent to a PHP echo, you'll want to use Javascript (or JQuery) DOM manipulation for that.
EDIT: I forgot to mention, the other option is simply to do all the PHP stuff on the server-side before you send the page at all, instead of AJAX you'd want to do something in PHP like including your other php script and calling methods from it. But, everything you do on the server-side, the user is sitting there looking at a blank screen waiting for the page to load. So this isn't an option for anything that's not very quick.
Related
I am working on a project where I used ajax for asynchronous DB access.
I store the value in JavaScript variable as follows..
var content=xmlhttp.responseText;
now what I wanted is to pass this value to the php module on same page..
Please suggest me..its urgent
You'll have to make a separate AJAX request to another script to achieve this. PHP is server-sided and therefore cannot directly interact with the client.
You should handle the data (which you are assigning to content) in PHP because, as the other answers here tell you, PHP is server-side and JavaScript is on the client. If you are getting this data from a page you control, instead of var content = xhr.responseText; just modify the data BEFORE you send it. For example, if you are making an AJAX call to a process.php file on your server to get the data you are otherwise assigning to content in JavaScript, be sure to handle the data in process.php PRIOR to echo()'ing the data (which you are then storing inside content on the client):
In process.php:
// below is the normal server script which you are storing in content on the client
// echo $result;
// instead, we are going to operate on the data first:
return doSomething($result);
Then on the client:
var newContent = xhr.responseText;
And the newContent variable will contain the data you previously wished to modify with PHP. If you DO NOT have control of the server script which you are calling with AJAX, then as mentioned here already, you will need to send a SECOND AJAX call to the server with your PHP, and use $_GET or $_POST to retrieve that content data and then play with it there.
Am unclear about your need to pass value from javascript to php.
But I can give you,
A non-recommended but working approach towards your problem:
You said, you are making an Ajax call at first. While processing the corresponding server side php function, Store the response value (value of xmlhttp.responseText) into a $_SESSION variable. Finally Reload the page (using location.reload()) inside the ajax response handler function.
And a recommended approach towards your problem:
You might have added some if-else control-flow structures in the php code and expecting to execute them after getting the ajax response value (sadly you cannot do that). So if you do have some logic like that, then convert those if-else conditions to corresponding Javascript code. May be a javascript function and call that function by passing the ajax response value to it. This new function will use your ajax response value and make changes in some parts of your webpage by applying necessary logic.
I have a Javascript variable which I am setting a PHP variable to.
function cancel(number) {
var message = "<?= $message[" + number + "]; ?>";
}
$message is an array. "number" is the element of the array I want to set message to. Basically, I want to set a Javascript variable to a PHP variable using a Javascript variable as the element picker. So if "number" was 2, it would select:
$message[2];
However, the above approach doesn't work, and I'm not even sure if this is possible.
It isn't. Use XHR to retrieve the value from the server.
It doesn't seem at all possible; PHP is evaluated server-side, and javascript is evaluated client-side. So PHP would see it as $message["+number+"], and try to find the value at the index of "+number+". You'd probably have to do something like an AJAX request to get the data you're looking for.
What you are doing isn't possible; since php is a server-side language, it's executed first, and the js is executed after; there isn't any way to control which is executed first. You must retrieve the variable using AJAX.
Something like this will work:
<script type="text/javascript">
var messages = <?= json_encode($message) ?>;
function cancel(number) {
var message = messages[number];
}
</script>
Of course this will output the entire array in the JavaScript source. If it is large, then you are better off using AJAX.
Tip: if you "view source" it should be painfully obvious why your method doesn't work.
You simply cannot do this using this methodology. PHP is server-side code, meaning that it runs on the server, while JavaScript is client-side code, meaning it runs on the client, or your browser.
Once the PHP runs, it generates an HTML document and sends that document in the response to the browser. Once that's complete, the only way you can get data back to the server is to send it via a form POST, send it via AJAX, or send it via script tag remoting.
Consider looking at some examples on the Internet of how to POST data back to the server via a form and via AJAX. It's clear you're struggling with some concepts regarding how to properly architect your program, and looking at some examples would be a great way for you to learn and master these techniques.
PHP Submit Form Example
PHP Tutorial
You need to use AJAX call to resolve your issue.
I the following code:
<? $test = new com("Soundclass.Soundrec"); ?>
<? $test->startrec ?>
<script>
function stop(){
var stop_record = "<?=$test->stoprec;?>";
}
</script>
and I am running the stop function in a button click. But the php function seems to run without the click.
The purpose of this is to stop the recording on that button click.
You have a little logical error:
PHP is server-side and gets executed on the server when the document is called.
Javascript is client-side and gets called dynamically, it can't re-execute any php-code again.
See the source code in your browser and you'll understand!
But you could make an ajax call to the class and execute the stoprec() method with a (defined in your script) get/post variable. But as this still won't give you a handle on the same instance of the object, so unfortunately you probably have to rethink your whole script!
What you are trying to do is fundamentally impossible: You are mixing up PHP (which runs on server side) and JavaScript (which runs on client side).
You would have to build a second PHP script that stops the recording, and have that called from JavaScript using Ajax.
Calling $test->stoprec will probably stop recording (don't know Soundclass.Soundrec that specifically myself).
As you call it even before the page has been delivered, pressing the stop button later won't make a change here.
You need to execute the PHP later (after button click), however you have the general problem here that the com object in $test won't survive that (it would be a new one).
The only solution I see here is that you create a daemon that manages sound recording for you. This would work with AJAX, but is not trivial. So the short (and sad) answer is: Not easily possible.
For example:
$(document).ready(function(){
$('.selector').click(function(){
<?php
// php code goes here
?>
});
});
Will this cause issues or slow down the page? Is this bad practice? Is there anything important that I should know related to this?
Thanks!
If you are trying to bound some PHP code with the click event then this is impossible in the way you are trying and PHP code will be executed as soon as page load without waiting for a click event.
If you are trying to generate final javascript or jquery code using PHP then this is okay.
It won't slow down the page; the PHP runs on the server and emits text which is sent to the browser, as on any PHP page. Is it bad practice? I wouldn't say "bad" necessarily, but not great. It makes for messy code - in the event where I need to do something like this, I usually try to break it up, as in:
<script>
var stuff = <?php print $stuff; ?>;
var blah = "<?php print $blah; ?>";
// Do things in JS with stuff and blah here, no more PHP mixed in
</script>
PHP is executed on the server, and then the javascript will be executed on the client. So what you'd be doing here is using php to generate javascript that will become the function body. If that's what you were trying to do then there's nothing wrong with doing it.
If you thought you were going to invoke some PHP code from javascript, then you're on the wrong track. You'd need to put the PHP code in a separate page and use an ajax request to get the result.
Sure, as long as you keep in mind that PHP code will be executed by the server before the page is sent out. Other than that, have fun.
PHP is a "backend" language and javascript is a "frontend" language. In short, as long as the PHP code is loaded through a web server that understands PHP - the downside is that you have to inline the JS, losing caching ability (there are workarounds to parse php in .js files but you shouldn't really do this). To the user it will just look like javascript and HTML. Here's the server order:
User requests page.
Apache (or equivalent) notices this
is a php file. It then renders all
the php that are between php tags.
Apache sends the page to the user.
User's browser sees the JavaScript
and executes it.
Just be sure the PHP is outputting valid JavaScript.
you have a better choice to use ajax that runs the php script when you are handling a click event
$(document).ready(function(){
$('.selector').click(function(){
$.ajax({url:"phpfile.php",type:"POST",
data:"datastring="+value+"&datastring2="othervalue,
,success:function(data){
//get the result from the php file after it's executed on server
}
});
});
});
No it's not. Just as long as you know that the JS is executed after the PHP page is parsed.
I want to call a PHP function when pressing on a button, sort of like:
<?php
function output(){
// do something
}
?>
<input type="button" value="Enter" onclick="output()"/>
I tried to make something like:
<input type="button" value="Enter" onclick="test.php?execute=1"/>
where test.php is current page and then by php
<? if(isset(&execute)){ echo "Hello"; } ?>
but it doesn't work.
Since PHP runs on the webserver, and buttons (and JavaScript in this case) appear on the client, you have to make an HTTP request to the server.
The easiest way to do this is to use a form. No JavaScript is required. You can add JavaScript (although it should be layered on top of a working non-JS version). Using JavaScript to make an HTTP request without leaving the page is known as Ajax, and generally achieved with the XMLHttpRequest object. There are various libraries such as YUI and jQuery that can do some of the heavy lifting for you.
I think using an AJAX call would do sort of what you are asking. I don't know PHP very well but you can use the following example, and add another variable with the data you are passing in to the server to indicate which function you want to call on the server. On the server you can add some "IF" statements that will call a certain function based on the name passed in and return the result.
Here is what you could use on in your javascript client using the jQuery library as a helper to do the AJAX call:
<input type="button" value="Enter" onclick="output()"/>
<script type="text/javascript">
function output(){
$.ajax({
type: "POST",
url: "submit_data.php",
data: "username=" + "SomeUser"
+ "&email=" + "someEmail#google.com"
+ "&functionName=" + "theFunction1",
success: function(html){
alert('sucess! Result is:' + html);
}
});
}
</script>
and you can use code such as this to catch the data your javascript is passing in. In this example you would want to call this file name as "submit_data.php" to match the javascript above:
<?php
// Variables
$Username = $_POST['username'];
$Email = $_POST['email'];
$FunctionName = $_POST['functionName'];
//Add code here to choose what function to call and echo the result
// If $FunctionName equals 'theFunction1' then execute theFunction1
// If $FunctionName equals 'theFunction2' then execute theFunction2
echo "You called A Page!";
?>
Here I am doing nothing with the "username" and "email" simply grabbing it and storing them into holding variables. But you can easily add extra functionality here, such as checking for a name of a function that you want to run.
PHP is server side and javascript is client side. So I'm not sure if that is really what you want to be doing??
Perhaps you could explain why you want to specifically call a php function?
I googled PHP function from button and found this question on webdeveloper.com
It doesn't use Javascript.
This is PHP you're talking about, not ASP.NET. In PHP, there is no such thing as a button click event. PHP runs entirely on the server and has absolutely no knowledge of client-side events.
Your first try won't work because the PHP code only runs when the page first loads. It does not run when you call a JavaScript function. Your second example won't work because JavaScript and PHP can't talk directly to eachother like that. Trying to directly call a PHP function from JavaScript just doens't make sense. Remember, PHP only runs on the server. By the time you get to the point where JavaScript can run, the PHP code has long since completed its work.
If you want to do something when a button is clicked, you have to explicitly make a request back to the server. You can do this by just POSTing the form as CTphpnwb suggested. Just be aware that this will reload the page and you will have to manually save and restore the page state, e.g. repopulate input boxes. There is no built-in magic that will do this for you.
Alternatively, you can get all AJAXy and do the POST in JavaScript. However, you will have to write the JavaScript to send the request and process the response, and write the server-side PHP code to handle the request. This gets a little awkward to do in a single page.
From : http://www.dreamincode.net/forums/showtopic72353.htm
You cannot directly invoke a PHP function from Javascript this way :
PHP code is executed on the server
HTML / Javascript are interpreted on the client-side.
One the HTML page has been generated and sent to the client (the browser), there is nothing more PHP can do.
One solution would be to use an Ajax request :
Your onclick event would call a Javascript function
This Javascript function would launch an Ajax request : a request sent to the server
The server would then execute some PHP code
And, then, return the result of that execution to the client
And you'd be able to get that result in your Javascript code, and act depending on what was returned by the server.
There are plenty of solutions to do an Ajax request :
You can re-invent the wheel ; not that complex, I should say -- but see the next point
If already using a Javascript framework, like jQuery, Prototype, ... Those provide classes/methods/functions to do Ajax requests
Googling a bit will get you lots of tutorials/examples, about that ;-)