Function to add adsense ads to WordPress theme with tracking codes per author and a default tracking code for non-post pages. Work in progress, but should function fine. Will be finished and made into a plugin when I have time. Adapted from what I did for http://NatureScholar.com Needs: a better way to set the Client ID, make into a plugin, more…

adsenser.php

<?php
//based on http://wp.tutsplus.com/tutorials/business/how-to-share-adsense-revenue-with-your-authors/
//Set Adsense client ID.
$ad_client_id = ' ';

// Create Custom Settings Menu
add_action('admin_menu', 'adsenser_menu');
function adsenser_menu() {
	//Create Sub-Level Menu Page under Settings
	add_submenu_page( 'options-general.php', 'Adsenser Settings', 'Adsenser', 'manage_options', 'adsenser_settings_page', 'adsenser_settings_page');
}
function adsenser_settings_page() {
	//must check that the user has the required capability
	if (!current_user_can('manage_options'))
	{
		wp_die( __('You do not have sufficient permissions to access this page.') );
	}
?>
<div class="wrap">
		<h2>Ad Share Settings</h2>
		<form method="post" action="options.php">
			<?php wp_nonce_field('update-options') ?>
			<p><strong>Default Channel:</strong><br />
				<input type="text" name="channel-id" size="45" value="<?php echo get_option('channel-id'); ?>" />
			</p>
			<p><input type="submit" name="Submit" value="Save" /></p>
			<input type="hidden" name="action" value="update" />
			<input type="hidden" name="page_options" value="channel-id" />
		</form>
	</div>
<?php
}
add_action( 'show_user_profile', 'adsenser_profile_fields' );
add_action( 'edit_user_profile', 'adsenser_profile_fields' );
function adsenser_profile_fields( $user ) { ?>
	<h3>Extra Field</h3>
	<table class="form-table">
		<tr>
			<th><label for="twitter">Adsense Channel:</label></th>
			<td>
				<input type="text" name="channel-id" id="channel-id" value="<?php echo esc_attr( get_the_author_meta( 'channel-id', $user->ID ) ); ?>" class="regular-text" /><br />
				<span class="description">Don't mess with this.</span>
			</td>
		</tr>
	</table>
<?php }
add_action( 'personal_options_update', 'adshare_save_profile_fields' );
add_action( 'edit_user_profile_update', 'adshare_save_profile_fields' );
function adshare_save_profile_fields( $user_id ) {
	if ( !current_user_can( 'edit_user', $user_id ) ){
		return false;
	}
	update_user_meta( $user_id, 'channel-id', $_POST['channel-id'] ); //
}
function adsenser_ad() {
    if(get_the_author_meta( 'channel-id' )){
        $input = array(get_option('channel-id'), get_the_author_meta( 'channel-id' ));
    }else{
        $input = array(get_option('channel-id'));
    }
    shuffle($input);
?>
<script type="text/javascript">
	<!--
	google_ad_client = "<?php echo $ad_client_id; ?>";
	google_ad_slot = "<?php echo $input[0]; ?>";
	google_ad_width = 120;
	google_ad_height = 600;
	//-->
</script>
<script type="text/javascript" src="http://pagead2.googlesyndication.com/pagead/show_ads.js"></script>
<?php
}
?>

instructions.txt

Instructions:
1) Add this file to your theme and include it in functions.php or paste the whole thing into function.php.

2) Insert your client ID on line 4Based on  as the value for $ad_client_id variable.

3) If necessary change dimensions of add on lines 66 and 67.

4) In your adsense account create tracking codes for each author and an extra as your default.

5) In WP go to the new Adsenser settings page and set the default tracking code.

6) For each author set there tracking code in their profile page.

7) Where ever you want the add to appear do this: <?php adsenser_ad(); ?>