Post rating using Custom Field

Question

First off, you should consider using using the building WordPress functionality rather than linking straight to a PHP file. Anyone could game that very easily and artificially vote up posts.

To use the wordpress ajax functionality, send your ajax request to yoursite.com/wp-admin/admin-ajax.php, and use standard plugin hooks system.

Tollmanz’s response is right on: your update post meta and get post meat calls aren’t working because the WordPress environment is not loaded in rating.php. Another reason to use admin-ajax.php to handled your response.

Here’s an example:

<?php
add_action( 'wp_ajax_nopriv_wpse26789_action', 'wpse26789_ajax_cb' );
add_action( 'wp_ajax_wpse26789_action', 'wpse26789_ajax_cb' );
function wpse26789_ajax_cb()
{
    // Verify the nonce to make sure the request came from an actual page...
    if( !isset( $_REQUEST['nonce'] ) || ! wp_verify_nonce( $_REQUEST['nonce'], 'wpse26789_nonce' ) ) die( '-1' );

    $post_id = isset( $_REQUEST['post_id'] ) ? absint( $_REQUEST['post_id'] ) : 0;

    if( ! $post_id ) die( '-1' );

    $counter = get_post_meta( $post_id, 'good_post', true );
    $counter = absint( $counter );

    if( $counter )
    {
        $counter++;
    }
    else
    {
        $counter = 1;
    }

    update_post_meta( $post_id, 'good_post', $counter );
    echo $counter;
    die();
}

Then your front end could would have to change a little bit.

Here’s a function you could drop inside the loop on your single.php file:

<?php 
function wpse26789_good_bad()
{
    global $post;
    $count = get_post_meta( $post->ID, 'good_post', true );
    ?>
    <p id="wpse26789_click">Click Here to Vote this Post up</p>
    <p>This post has <span id="wpse26789_count"><?php echo strip_tags( $count ); ?></span> votes</p>
    <?php
}

Eg. somewhere in single.php insert wpse26789_good_bad() or insert the code from the function into single.php (except for the global $post) anywhere inside the loop.

Then you’ll need to change up your javascript a bit. I’ve just hooked into wp_head here to add the javascript to the <head> section of any singular post.

<?php
add_action( 'wp_head', 'wpse26789_head' );
function wpse26789_head()
{
    if( ! is_singular() ) return;
    $post_id = get_queried_object_id();
    ?>
    <script type="text/javascript">
        var wpse26789_data = {
            action: 'wpse26789_action',
            post_id: '<?php echo absint( $post_id ); ?>',
            nonce: '<?php echo wp_create_nonce( 'wpse26789_nonce' ); ?>',
        }
        jQuery(document).ready(function(){
            jQuery( '#wpse26789_click' ).click(function(){
                jQuery.get( 
                    '<?php echo site_url( 'wp-admin/admin-ajax.php' ); ?>', 
                    wpse26789_data, 
                    function( data ){
                        if( '-1' != data )
                        {
                            jQuery( 'span#wpse26789_count' ).html( data );
                            alert( 'Your Message!' );
                        }
                    }
                );
            });
        });
    </script>
    <?php
}

As a plugin: http://pastie.org/2423993