Troubleshooting “Warning: session_start(): Cannot send session cache limiter - headers already sent”

Question

i am getting Warning: session_start() [function.session-start]: Cannot send session cache limiter - headers already sent (output started at error

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Answer 1

This should solve your problem. session_start() should be called before any character is sent back to the browser. In your case, HTML and blank lines were sent before you called session_start(). Documentation here.

To further explain your question of why it works when you submit to a different page, that page either do not use session_start() or calls session_start() before sending any character back to the client! This page on the other hand was calling session_start() much later when a lot of HTML has been sent back to the client (browser).

The better way to code is to have a common header file that calls connects to MySQL database, calls session_start() and does other common things for all pages and include that file on top of each page like below:

include "header.php";

This will stop issues like you are having as also allow you to have a common set of code to manage across a project. Something definitely for you to think about I would suggest after looking at your code.

<?php
session_start();

                if (isset($_SESSION['error']))

                {

                    echo "<span id=\"error\"><p>" . $_SESSION['error'] . "</p></span>";

                    unset($_SESSION['error']);

                }

                ?>

                <form action="<?php echo $_SERVER['PHP_SELF']; ?>" method="post" enctype="multipart/form-data">

                <p>
                 <label class="style4">Category Name</label>

                   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <input type="text" name="categoryname" /><br /><br />

                    <label class="style4">Category Image</label>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

                    <input type="file" name="image" /><br />

                    <input type="hidden" name="MAX_FILE_SIZE" value="100000" />

                   <br />
<br />
 <input type="submit" id="submit" value="UPLOAD" />

                </p>

                </form>




                             <?php



require("includes/conn.php");


function is_valid_type($file)

{

    $valid_types = array("image/jpg", "image/jpeg", "image/bmp", "image/gif", "image/png");



    if (in_array($file['type'], $valid_types))

        return 1;

    return 0;
}

function showContents($array)

{

    echo "<pre>";

    print_r($array);

    echo "</pre>";
}


$TARGET_PATH = "images/category";

$cname = $_POST['categoryname'];

$image = $_FILES['image'];

$cname = mysql_real_escape_string($cname);

$image['name'] = mysql_real_escape_string($image['name']);

$TARGET_PATH .= $image['name'];

if ( $cname == "" || $image['name'] == "" )

{

    $_SESSION['error'] = "All fields are required";

    header("Location: managecategories.php");

    exit;

}

if (!is_valid_type($image))

{

    $_SESSION['error'] = "You must upload a jpeg, gif, or bmp";

    header("Location: managecategories.php");

    exit;

}




if (file_exists($TARGET_PATH))

{

    $_SESSION['error'] = "A file with that name already exists";

    header("Location: managecategories.php");

    exit;

}


if (move_uploaded_file($image['tmp_name'], $TARGET_PATH))

{



    $sql = "insert into Categories (CategoryName, FileName) values ('$cname', '" . $image['name'] . "')";

    $result = mysql_query($sql) or die ("Could not insert data into DB: " . mysql_error());

  header("Location: mangaecategories.php");

    exit;

}

else

{





    $_SESSION['error'] = "Could not upload file.  Check read/write persmissions on the directory";

    header("Location: mangagecategories.php");

    exit;

}

?> 

Answer 2

For others who may run across this - it can also occur if someone carelessly leaves trailing spaces from a php include file. Example:

 <?php 
    require_once('mylib.php');
    session_start();
 ?>

In the case above, if the mylib.php has blank spaces after its closing ?> tag, this will cause an error. This obviously can get annoying if you've included/required many files. Luckily the error tells you which file is offending.

HTH

Answer 3

This started for me when I redirected my site to https:// (for SSL Certificate). From my experience with this issue, the session_start() had to be before the browser saw any HTML code. For my example, I was using session_start() in nav.php to determine the options of the navigation bar. I ended up placing session_start() right after the php comments in the index.php file and every page which called nav.php. I was able to keep the php comments before session_start() but could not keep the HTML comments above the php.

Answer 4

I was able to solve similar Warning: session_start(): Cannot send session cache limiter - headers already sent by just removing a space in front of the <?php tag.

It worked.

Answer 5

replace session_start(); with @session_start(); in your code

Answer 6

I had the same issue, but my solution wasn't as obvious as the suggested ones. It turned out that my php-file was written in UTF-8, which caused issues. I copy/pasted the content of the entire file into a new php-file (Notepad++ tells me this is written in ANSI rather than UTF-8), and now it work flawlessly.