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POWhy am I getting this PHP session_start() error?
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  1. POWhy am I getting this PHP session_start() error?
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    copied!<p>I can not figure out why I am getting this session error... </p> <blockquote> <p>Warning: session_start() [function.session-start]: Cannot send session cache limiter - headers already sent (output started at C:\webserver\htdocs\project2\labs\form-submits\index.php:2) in C:\webserver\htdocs\project2\labs\form-submits\index.php on line 2</p> </blockquote> <p>As far as I knew this happens only when there is some sort of output to the browser before the session_start() function is called, in this case there is nothing printed to screen before the call, not even any white space. Any ideas why I would still get the errors? </p> <p>I posted the full source code of this demo so you can see exactly what I used to create the error.</p> <pre><code>&lt;?php session_start(); require('formkey.class.php'); $formKey = new formKey(); $error = 'No error'; //Is request? if($_SERVER['REQUEST_METHOD'] == 'post') { //Validate the form key if(!isset($_POST['form_key']) || !$formKey-&gt;validate()) { //Form key is invalid, show an error $error = 'Form key error!'; } else { //Do the rest of your validation here $error = 'No form key error!'; } } ?&gt; &lt;!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"&gt; &lt;html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"&gt; &lt;head&gt; &lt;meta http-equiv="content-type" content="text/html;charset=UTF-8" /&gt; &lt;title&gt;Securing forms with form keys&lt;/title&gt; &lt;/head&gt; &lt;body&gt; &lt;div&gt;&lt;?php if($error) { echo($error); } ?&gt; &lt;form action="" method="post"&gt; &lt;dl&gt; &lt;?php $formKey-&gt;outputKey(); ?&gt; &lt;dt&gt;&lt;label for="username"&gt;Username:&lt;/label&gt;&lt;/dt&gt; &lt;dd&gt;&lt;input type="text" name="username" id="username" /&gt;&lt;/dd&gt; &lt;dt&gt;&lt;label for="username"&gt;Password:&lt;/label&gt;&lt;/dt&gt; &lt;dd&gt;&lt;input type="password" name="password" id="password" /&gt;&lt;/dd&gt; &lt;dt&gt;&lt;/dt&gt; &lt;dd&gt;&lt;input type="submit" value="Submit" /&gt;&lt;/dd&gt; &lt;dl&gt; &lt;/form&gt; &lt;/body&gt; &lt;/html&gt; </code></pre> <p>the class file</p> <pre><code>&lt;?php class formKey { //Here we store the generated form key private $formKey; //Here we store the old form key private $old_formKey; //The constructor stores the form key (if one excists) in our class variable function __construct() { //We need the previous key so we store it if(isset($_SESSION['form_key'])) { $this-&gt;old_formKey = $_SESSION['form_key']; } } //Function to generate the form key private function generateKey() { $ip = $_SERVER['REMOTE_ADDR']; $uniqid = uniqid(mt_rand(), true); return md5($ip . $uniqid); } //Function to output the form key public function outputKey() { //Generate the key and store it inside the class $this-&gt;formKey = $this-&gt;generateKey(); //Store the form key in the session $_SESSION['form_key'] = $this-&gt;formKey; //Output the form key echo "&lt;input type='hidden' name='form_key' id='form_key' value='".$this-&gt;formKey."' /&gt;"; } //Function that validated the form key POST data public function validate() { //We use the old formKey and not the new generated version if($_POST['form_key'] == $this-&gt;old_formKey) { //The key is valid, return true. return true; } else { //The key is invalid, return false. return false; } } } ?&gt; </code></pre>
 

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