Weird behavior with a class level variable - php

Question

I've looked at this code for over an hour, and it looks fine to me. However, the description variable is losing scope when I use the insertSubmit() function. The variable is set during construction but not when I use the insertSubmit(). Am I missing something here?
<?php session_start();
class SubmitNew {
var $title = "";
var $category = "";
var $summary = "";
var $description = "";
var $username = "";
var $timestamp = "";
var $errors = "";
var $errorStr = "";
var $link = "";
var $db = "";
public function __construct() {
$this->setVariables();
$this->errors = 0;
$this->p_id = 1;
}
public function setVariables() {
$this->title = "1";
$this->category = "2";
$this->summary = "3";
$this->description = "4";
echo $this->description;
$this->timestamp = mktime(date("G"), date("i"),
date("s"), date("m") , date("d"), date("Y"));
}
public function errorBlank() {
if($this->title == null) {
$this->errorStr = $this->errorStr."blanktitle";
$this->errors++;
} if($this->summary == null) {
$this->erroStr = $this->errorStr."blanksummary";
$this->errors++;
} if($this->description = null) {
$this->erroStr = $this->errorStr."blankdescription";
$this->errors++;
}
}
public function errorAll() {
if($this->errors == 0) {
return "success";
} else {
return $this->errorStr;
}
}
public function insertSubmit() {
echo $this->description;
}
}

Answer 1

The problem is located at errorBlank() function, when you do this:
} if($this->description = null) {
Instead of doing this:
} if($this->description == null) {
Note the extra equal sign! You were assigning null to $this->description, instead of comparing them!