php - parse_str randomly adding semicolons to keys


I am passing a query string as part of my query string to a PHP script.

Kinda like this:

$.post('/url', {
    id: postID
    filters: $('#form').serialize()

Then in my PHP, I useparse_str to readfilters:

$postID = $this->input->post('id');
parse_str($this->input->post('filters'), $filters);

The problem is thatparse_str is adding;s randomly to the keys. I'm getting a result like this:

array(4) {
  string(0) ""
  string(0) ""
  string(0) ""
  array(2) {
    string(4) "1234"
    string(4) "5678"

Why is the server adding;? I tried it on another server, and this doesn't happen. It also doesn't happen when testing via CLI.

EDIT: Seems this is notparse_str's fault, but some sort of XSS filter.$this->input->post('filters') (and even$_POST['filters']!) contains the; characters. I checked, and jQuery is not adding them.

EDIT: I managed to "fix" this by doing:

$filters = array_combine(array_map(function($x){
    return str_replace(';', '', $x);
}, array_keys($filters)), array_values($filters));



This is caused by the config variableglobal_xss_filtering in Codeigniter. Set it to false to disable this behaviour.

See also:
xss_clean adds semicolon to anything with an &
CodeIgniter adding semicolons




I would first do a var_dump of the $filters to see what is coming in.

parse_str will parse the string you send it like so:

$string = "user=&companies=StackOverflow";
parse_str($string, $filters);
echo $filters['user']; // empty string
echo $filters['companies']; // StackOverflow

My best guess is that what is being sent from iQuery's serialize (inclusive of the data) is not properly serialized/escaped probably so parse_str can easily split the string with the & as the separator for key/value of each parameter.

Reading the manuals you are definitely doing things correctly there but there might be something lurking in your data that throws the parse_str off. I would also look for illegal characters in the sting posted by jQuery.

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