function 'save_details' not found, Warning

Hello

Long time reader, first time caller.
I am getting the following warning when saving posts, customs posts in the admin, it has to with this line: add_action('save_post', 'save_details');

The error I get is:Warning: call_user_func_array() expects parameter 1 to be a valid callback, function ‘save_details’ not found or invalid function name in /home/mccrudde/public_html/newsite/wp-includes/plugin.php on line 406

Warning: call_user_func_array() expects parameter 1 to be a valid callback, function ‘save_details’ not found or invalid function name in /home/mccrudde/public_html/newsite/wp-includes/plugin.php on line 406

Warning: Cannot modify header information – headers already sent by (output started at /home/mccrudde/public_html/newsite/wp-includes/plugin.php:406) in /home/mccrudde/public_html/newsite/wp-includes/pluggable.php on line 876

Now the URL rewrite works perfectly, but, updating the post give the error warning and noting else, however changes to the post content are saved. Also I don’t get this error on my local host just online ‘both V3.5.1″

I have pasted below the full CPT function code.

add_action('init', 'trainingcourses');

function trainingcourses() {

     register_taxonomy(
        'coursesector',
        'trainingcourses',
        array(
            'label' => 'Training Sectors',
            'singular_label' => 'Type',
            'hierarchical' => true,
            'query_var' => true,
            'rewrite' => array('slug' => 'training'),
        )
    );

    $labels = array(
        'name' => _x('Training Courses', 'post type general name'),
        'singular_name' => _x('Sector', 'post type singular name')
    );

    $args = array(
        'labels' => $labels,
        'public' => true,
        'publicly_queryable' => true,
        'show_ui' => true,
        'query_var' => true,
        'capability_type' => 'post',
        'hierarchical' => false,
        'menu_position' => 6,
        'supports' => array('title','editor','thumbnail', 'excerpt'),
        'rewrite' => array(
            //'slug' => 'training',
            'slug' => 'training/%coursesector%',
            'with_front' => false
        ),
        'has_archive' => 'training'
    ); 

    register_post_type( 'trainingcourses' , $args );
    flush_rewrite_rules();
}

add_action('save_post', 'save_details');

add_filter('post_type_link', 'training_permalink_structure', 10, 4);
function training_permalink_structure($post_link, $post, $leavename, $sample)
{
    if ( false !== strpos( $post_link, '%coursesector%' ) ) {
        $coursesector_term = get_the_terms( $post->ID, 'coursesector' );
        $post_link = str_replace( '%coursesector%', array_pop( $coursesector_term )->slug, $post_link );
    }
    return $post_link;
}

this problem on occurs witin the admin, as I say the site front-end works fine. but I can’t hand over to client with the error screen. I have looked for hours for a solution, but I’m not a coder so am struggling, any help gratefully received.