uninstall.php

<?php
/**
 * Fired when the plugin is uninstalled
 *
 * @package Contextual_Related_Posts
 */

if ( !defined( 'WP_UNINSTALL_PLUGIN' ) ) {
    exit();
}


global $wpdb;

$option_name = 'ald_crp_settings';

if ( !is_multisite() ) {

	$wpdb->query( "ALTER TABLE " . $wpdb->posts . " DROP INDEX crp_related" );
	$wpdb->query( "ALTER TABLE " . $wpdb->posts . " DROP INDEX crp_related_title" );
	$wpdb->query( "ALTER TABLE " . $wpdb->posts . " DROP INDEX crp_related_content" );

	$wpdb->query("
		DELETE FROM " . $wpdb->postmeta . "
		WHERE meta_key='crp_related_posts'
	");

	$wpdb->query("
		DELETE FROM " . $wpdb->postmeta . "
		WHERE meta_key='crp_related_posts_widget'
	");

    delete_option( $option_name );

} else {

    // Get all blogs in the network and activate plugin on each one
    $blog_ids = $wpdb->get_col( "
    	SELECT blog_id FROM $wpdb->blogs
		WHERE archived = '0' AND spam = '0' AND deleted = '0'
	" );
    foreach ( $blog_ids as $blog_id ) {
    	switch_to_blog( $blog_id );

		$wpdb->query( "ALTER TABLE " . $wpdb->posts . " DROP INDEX crp_related" );
		$wpdb->query( "ALTER TABLE " . $wpdb->posts . " DROP INDEX crp_related_title" );
		$wpdb->query( "ALTER TABLE " . $wpdb->posts . " DROP INDEX crp_related_content" );

		$wpdb->query("
			DELETE FROM " . $wpdb->postmeta . "
			WHERE meta_key='crp_related_posts'
		");

		$wpdb->query("
			DELETE FROM " . $wpdb->postmeta . "
			WHERE meta_key='crp_related_posts_widget'
		");

	    delete_option( $option_name );

	}

    // Switch back to the current blog
    restore_current_blog();

}
?>