How do I make my plugin load before the headers are output so I can redirect wordpress?

Question

I wrote some code, that helps secure my clients files, and added it to wordpresses function file. however, whenever updates come in, it obviously overwrites my function.

So I wanted to create it as a plugin.

However, I keep getting this error:

PHP Warning:  Cannot modify header information - headers already sent by...

So I need to execute my code, BEFORE wordpress sends the headers.

How do I do that?

Thanks, Richard

Update. Okay, here is the code, I changed the tags though, but same premise...

<?php 
/*
 * Plugin Name: My WP Plugin
 * Plugin URI: http://www.example.com/plugins
 * Description: My Plugin
 * Version: 1.0
 * Author: My Name
 * Author URI: http://www.example.com/
*/

function somebit_init() {
    $_permaStruc = get_option('permalink_structure');
    if($_permaStruc != "") {
        if($_GET['dl']) {
            header("Location: http://google.com");
            exit;
        } else if($_GET['download']) {
            header("Location: http://google.com");
            exit;
        }
    }
}
add_action('init', 'somebit_init');
?>

I'm still getting the "PHP Warning: Cannot modify header information - headers already sent by..." error.

Do you see why? I cannot find it. maybe I did something wrong that I cannot see.

Richard

Answer 1

The correct hook to use is template_redirect which allows you to have the necessary info available to do checks while also early enough to actually redirect. As per the example on the codex page:

function my_page_template_redirect()
    {
    if( is_page( 'goodies' ) && ! is_user_logged_in() )
    {
        wp_redirect( home_url( '/signup/' ) );
        exit();
    }
}
add_action( 'template_redirect', 'my_page_template_redirect' );

Codex page here - template_redirect

Answer 2

How about using this action? Codex Link - send_headers action

add_action( 'send_headers', 'add_redirect_header' );
function add_redirect_header() {
    header( 'Location: http://www.google.com' );
}

Answer 3

use add_action('init', 'your_function');

or any action hook before headers are sent: http://codex.wordpress.org/Plugin_API/Action_Reference

Answer 4

Your checks, if($_GET['dl']) and else if($_GET['download']) are throwing Undefined index: errors, and that appears to be causing a headers issue with your My Security Plugin.

Try changing it to:

function somebit_init() {
    $_permaStruc = get_option('permalink_structure');
    if($_permaStruc != "") {
        if( !empty($_GET['dl'])) {
            header("Location: http://google.com");
            exit;
        } else if( !empty($_GET['download'])) {
            header("Location: http://google.com");
            exit;
        }
    }
}

Answer 5

This is a function I used to check if a non logged in user is trying to enter directly in custom page (only for users), it check if someone entered certain page.

Even makes a second check if the main cookies are created (useful to avoid undefined index errors)

    function validate_sesion() {
    if ((is_page('something'))||(is_singular('something'))) {
        if (!is_user_logged_in()) {
            wp_redirect(home_url('log-out'));
            exit();
        } elseif ((empty($_COOKIE["user_id"])) || (empty($_COOKIE["user_role"]))) {
            if (is_user_logged_in()) {
                wp_redirect(home_url('log-out'));
                exit();
            }
        }
    }

Just like the other answers, I used the 'template_redirect' hook

    add_action('template_redirect', 'validate_sesion');

I hope it can help someone