boolean variables posted through AJAX being treated as strings in server side - php

Question

Following is a part of an AJAX functionality to add classes and packs to session cart:-
The jquery part
function addClassToCart(itemId)
{
addItemToCart(itemId,true);
}
function addPackToCart(itemId)
{
addItemToCart(itemId,false);
}
function addItemToCart(itemId,isClass)
{
$.post(url+"/ajax/add_cart", { operation: 'add_cart','isClass':isClass, 'itemId': itemId},
function(data)
{
if(data.success)
{
alert("item added to cart");
}
}, "json");
}
The AJAX request processing php part -
//Checking operation and other posted parameters
if($_POST['isClass'])
{
//Code to add class to session cart
}
else
{
//Code to add pack to session cart
}
The strange thing
No matter whether I pass true/false (by calling addClassToCart() and addPackToCart()), always the code to add class to session cart executes.
If I put echo statements there like this:-
if($_POST['isClass'])
{
echo "see if condition ".$_POST['isClass'];
}
else
{
echo "see else condition ".$_POST['isClass'];
}
This is the output:-
addClassToCart() see if condition true
addPackToCart() see if condition false
Putting conditions like this in the jquery code however works fine:-
function addItemToCart(itemId,isClass)
{
if(isClass)
alert("is class");
else
alert("is pack");
}
Finally, if I alter the server side code to this:-
if($_POST['isClass'] === true)
{
echo "see if condition ".$_POST['isClass'];
}
else
{
echo "see else condition ".$_POST['isClass'];
}
These are the outputs -
addClassToCart() see else condition true
addPackToCart() see else condition false
So, why is the boolean variable treated as a string here? Am I doing something wrong in posting parameters?
Thanks,
Sandeepan

Answer 1

Also you can use filter_var function with filter FILTER_VALIDATE_BOOLEAN. According to php documentation it
Returns TRUE for "1", "true", "on" and "yes". Returns FALSE otherwise. If FILTER_NULL_ON_FAILURE is set, FALSE is returned only for "0", "false", "off", "no", and "", and NULL is returned for all non-boolean values.
So receiving of POST parameter will look like:
$isClass = filter_var($_POST['isClass'], FILTER_VALIDATE_BOOLEAN);

Answer 2

You aren't doing anything wrong per se, it's just that when it gets posted, it looks like this:
operation=add_cart&isClass=true&itemId=1234
PHP can't tell what the data type is because it isn't passed, it's always just a string of POST data, so compare it to "true" to do your checks, like this:
if($_POST['isClass'] === "true")
{
//Code to add class to session cart
}
else
{
//Code to add pack to session cart
}

Answer 3

This is a bit of an old question, but I'm surprised nobody has posted this here as solution.
Just use 1 and 0 instead of true and false when you're constructing your ajax requests.
When you do a == comparison, they'll be interpreted as true/false.
JS:
$.ajax({
url: '....',
data: {
foo: 1,
bar: 0
}
});
PHP:
<?php
if ($_GET['foo']) {
//...
} else {
//...
}
echo $_GET['bar'] ? 'bar is true' : 'bar is false';
?>

Answer 4

Send the data from your javascript as stringified JSON.
Make a PHP function to convert the strings 'true' and 'false' to boolean value.
Personally I like #2, which goes with Nick Craver's answer.