Wordpress - Fatal error: Call to a member function get_var() on a non-object $wpdb

Question

[Solution by s_ha_dum on http://wordpress.stackexchange.com]

I'm trying to direct users to a certain post based on a password entered in post settings. I have almost working code:

Form on page:

<form method="post" action="">
  <input type="password" name="passwordfield">
  <input type="hidden" name="homepagepassword" value="1">
  <input type="submit" value="Submit">
</form>

Code in functions.php

function doPasswordStuff(){
    if(isset($_POST['homepagepassword'])){
    $post_password = $_POST['passwordfield'];
    $post_id = $wpdb->get_var( $wpdb->prepare("SELECT ID FROM $wpdb->posts WHERE post_password = %s", $post_password) );
    $q = new WP_Query( 'p=$post_id' );
    if($q->have_posts()){
        while($q->have_posts()){
            $q->the_post();
            wp_redirect(get_permalink());
            die();
        }
    } else {
        // oh dear, there isnt a post with this 'password', put a redirect to a fallback here
        wp_redirect('http://www.google.com');
        die();
    }
    wp_reset_query();
    }
}
add_action('init','doPasswordStuff');

However I'm getting fatal error (Fatal error: Call to a member function get_var() on a non-object) on this line:

$post_id = $wpdb->get_var( $wpdb->prepare("SELECT ID FROM $wpdb->posts WHERE post_password = %d", $post_password) );

If would really appreciate if someone would take a look :) thanks!

Answer 1

globalize $wpdb before this

global $wpdb

$post_id = $wpdb->get_var( $wpdb->prepare("SELECT id FROM $wpdb->posts WHERE post_password = %s", $post_password) ); $q = new WP_Query( 'p=$post_id' );

Also it is a best practise to use lowercase table/column names

and then redirect like so

<?php if ( $q->have_posts() ) : while ( $q->have_posts() ) : $q->the_post(); ?>

wp_redirect( the_permalink() );

<?php endif;?>

Also use a http status code as the second parameter to wp_redirect() This might be helpful HTTP STATUS CODES