PHP JSON String Malformed - php

Question

I have a function which cleans users input. After the clean input is returned, it goes through json_decode($var, true); Currently, I'm getting an error of malformed string. Though, if I print it out and test with it http://jsonlint.com/, it passes. I've come to realize that the string after the cleansing processes is 149chars long, and before, its 85. To fix this, I also ran it through a regex to remove special characters, but I'm thinking that may undo what the previous function did. Does the "new" function undo what filer_var does? Is this the best way to clean input? Below is my code:
#index.php
$cleanInput = cleanse->cleanInput($_POST);
#cleanse.php OLD
function cleanInput($input){
foreach($input as $key => $value){
$cleanInput[$key] = filter_var($value, FILTER_SANITIZE_STRING, FILTER_FLAG_STRIP_HIGH));
}
return($cleanInput); //Returns 149char long string, visually 85chars
}
#cleanse.php NEW
function cleanInput($input){
foreach($input as $key => $value){
$cleanInput[$key] = preg_replace("[^+A-Za-z0-9]", "", filter_var($value, FILTER_SANITIZE_STRING, FILTER_FLAG_STRIP_HIGH)));
}
return($cleanInput); //Returns 85char long string, visually 85chars
}
#outputs
#Before
{"name":"Pete Johnson","address":"123 main street","email":"myemail#gmail.com","password":"PA$$word"}
#After
{"name":"Pete Johnson","address":"123 main street","email":"myemail#gmail.com","password":"PA$$word"}

Answer 1

The function call to filter_var($value, FILTER_SANITIZE_STRING, FILTER_FLAG_STRIP_HIGH) creates an output like this:
{"name":"Pete Johnson","address":"123 mainstreet","email":"myemail#gmail.com","password":"PA$$word"}
That is why json_decode does not work.
Like I said in the comments. Your best bet is to use json_decode on the input initially and then run through the individual elements with HTML_Purifier and or Zend_Validator or write your own to deal with individual fields. For example, email has different validation requirements than password.
EDIT:
I tried running through the new function, but I couldn't get it to work is. So I made a few adjustments to get it to work. Although I'm not sure if that was what you intended for your regex. Here is what I got as output from the this code:
$input = '{"name":"Pete Johnson","address":"123 main street","email":"myemail#gmail.com","password":"PA$$word"}';
$cleanedInput = preg_replace("/[^+A-Za-z0-9]/", "", filter_var($input, FILTER_SANITIZE_STRING, FILTER_FLAG_STRIP_HIGH));
echo $cleanedInput;
Output:
34name3434PeteJohnson3434address3434123mainstreet3434email3434myemailgmailcom3434password3434PAword34