PHP Post variable not working - php

Question

I am sending data to a PHP script using an android app. The following is the PHP script.
telejoke.php:
<?php
include 'JokeValidation.php';
include 'DBConnect.php';
$username = $_POST['username'];
$joke = $_POST['joke'];
$dbname = 'Telejoke';
mysql_select_db($dbname);
if (validate()){
$query = "INSERT INTO jokes (username, joke) VALUES ('$username','$joke')";
mysql_query($query) or die('Error, insert query failed');
}
mysql_close($conn);
?>
jokevalidation.php:
<?php
include 'DBConnect.php';
$dbname = 'telejoke';
mysql_select_db($dbname);
function validate(){
if ($joke == null) return false;
else if($username == null) return false;
return true;
}
?>
For some reason, the PHP script will put the data into the database when I take out if ($joke == null) return false; and else if($username == null) return false;. But when I put these statements into the PHP code, it seems that validate returns false. This is weird because $username and $joke will go to my database when I take out these statements meaning they cannot be null!.
Help is appreciated. Thanks.

Answer 1

Your validate function needs to have access to the $joke and $username objects.
function validate($joke, $validate) {
if ($joke == null)
return false;
else if ($username == null)
return false;
return true;
}
You can also get access to these variables by using the following inside your validate method:
global $joke, $username
However, it is better to declare what you're validating rather than relying on those variables being declared and set elsewhere in your code. Using global might fail silently for other reasons.

Answer 2

Variables have function scope. The variables $joke and $username do not exist inside the function, because you have neither declared nor passed them into the function. Use function parameters:
function validate($joke, $username) {
...
}
if (validate($joke, $username)) {
...
}

Answer 3

function validate($joke,$username)
also, filter those postvars before inserting them into your db.