if ($rating == "5.0"){ print("<IMG SRC ="stars/5-0.png>");}

<?php
$prefix = 'pk_rs_';

DEFINE ('PK_RS_DEFAULT_RATING', '-');

DEFINE ('PK_RS_DISPLAY', true);

$pk_rs_meta_box = array(
    'id' => 'pk_rich_snippet_review',
    'title' => 'Google Rich Snippets: Reviews',
    'page' => 'post',
    'context' => 'normal',
    'priority' => 'high',
    'fields' => array(
        array(
            'name' => 'Rating',
            'desc' => 'Product rating, from 1 to 5.',
            'id' => 'rating',
            'type' => 'select',
            'options' => array('-', '1.0', '1.5', '2.0', '2.5', '3.0', '3.5', '4.0', '4.5', '5.0')
        ),
        array(
            'name' => 'Author',
            'desc' => 'Author display name.',
            'id' => 'author',
            'type' => 'text',
            'std' => ''
        )

    )
);

add_action('admin_menu', 'pk_rich_snippet_add_box');

// Add meta box
function pk_rich_snippet_add_box() {
    global $pk_rs_meta_box;

    add_meta_box($pk_rs_meta_box['id'], $pk_rs_meta_box['title'], 'pk_rich_snippet_show_box', $pk_rs_meta_box['page'], $pk_rs_meta_box['context'], $pk_rs_meta_box['priority']);
}

// Callback function to show fields in meta box
function pk_rich_snippet_show_box() {
    global $pk_rs_meta_box, $post;

    // Use nonce for verification
    echo '<input type="hidden" name="pk_rich_snippet_nonce" value="', wp_create_nonce(basename(__FILE__)), '" />';

    echo '<table class="form-table">';

    foreach ($pk_rs_meta_box['fields'] as $field) {
        // get current post meta data
        $meta = get_post_meta($post->ID, $field['id'], true);

        echo '<tr>',
                '<th style="width:20%"><label for="', $field['id'], '">', $field['name'], '</label></th>',
                '<td>';
        switch ($field['type']) {
            case 'text':
                echo '<input type="text" name="', $field['id'], '" id="', $field['id'], '" value="', $meta ? $meta : $field['std'], '" size="30" style="width:97%" />',
                    '<br />', $field['desc'];
                break;
            case 'textarea':
                echo '<textarea name="', $field['id'], '" id="', $field['id'], '" cols="60" rows="4" style="width:97%">', $meta ? $meta : $field['std'], '</textarea>',
                    '<br />', $field['desc'];
                break;
            case 'select':
                echo '<select name="', $field['id'], '" id="', $field['id'], '">';
                foreach ($field['options'] as $option) {
                    echo '<option', $meta == $option ? ' selected="selected"' : '', '>', $option, '</option>';
                }
                echo '</select>', '<br />', $field['desc'];
                break;
            case 'radio':
                foreach ($field['options'] as $option) {
                    echo '<input type="radio" name="', $field['id'], '" value="', $option['value'], '"', $meta == $option['value'] ? ' checked="checked"' : '', ' />', $option['name'];
                }
                break;
            case 'checkbox':
                echo '<input type="checkbox" name="', $field['id'], '" id="', $field['id'], '"', $meta ? ' checked="checked"' : '', ' />',
                '<br />', $field['desc'];
                break;
        }
        echo    '<td>',
            '</tr>';
    }

    echo '</table>';
}

add_action('save_post', 'pk_rs_save_data');

// Save data from meta box
function pk_rs_save_data($post_id) {
    global $pk_rs_meta_box;

    // verify nonce
    if (!wp_verify_nonce($_POST['pk_rich_snippet_nonce'], basename(__FILE__))) {
        return $post_id;
    }

    // check autosave
    if (defined('DOING_AUTOSAVE') && DOING_AUTOSAVE) {
        return $post_id;
    }

    // check permissions
    if ('page' == $_POST['post_type']) {
        if (!current_user_can('edit_page', $post_id)) {
            return $post_id;
        }
    } elseif (!current_user_can('edit_post', $post_id)) {
        return $post_id;
    }

    foreach ($pk_rs_meta_box['fields'] as $field) {
        $old = get_post_meta($post_id, $field['id'], true);
        $new = $_POST[$field['id']];

        if ($new && $new != $old) {
            update_post_meta($post_id, $field['id'], $new);
        } elseif ('' == $new && $old) {
            delete_post_meta($post_id, $field['id'], $old);
        }
    }
}

add_filter('the_content', 'pk_rs_add_rich_snippet_to_content', 20);
function pk_rs_add_rich_snippet_to_content($content){
    if (is_single()&&!is_feed()){
        global $post;
        $rating = get_post_meta($post->ID, 'rating', true);
        $rating = ( '-' == $rating && '-' != PK_RS_DEFAULT_RATING ) ? PK_RS_DEFAULT_RATING : $rating;
        if ( '-' != $rating ){
            $title = $post->post_title ;
            $dateTime = date_create( $post->post_date );
            $date = $dateTime->format("Y-m-d");
            $date_only = $dateTime->format("M j");
            $author = get_post_meta($post->ID, 'author', true);
            $author = ( '' == $author ) ? ucfirst(get_the_author_meta('display_name', $post->post_author)) : $author;
            $summary = get_post_meta($post->ID, 'summary', true);
            $description = get_post_meta($post->ID, 'description', true);
            if ( !PK_RS_DISPLAY ) {
                $output = "<div class="hreview" style="display:none">";
                $output .= "<span class="item"><span class="fn entry-title">".$title."</span></span>";
                $output .= "Reviewed by <span class="reviewer">".$author."</span> on <span class="dtreviewed"> ".$date_only."<span class="value-title" title="".$date.""></span></span>";
                $output .= "Rating: <span class="rating">".$rating."</span>";
                $output .= "<span class="summary">".$summary."</span>";
                $output .= "<span class="description">".$description."</span>";
                $output .= "</div>";
            } else {
                $output = "<div class="hreview" style="display:block; margin: 0 0 10px 10px; padding: 10px; background: #F6F6F6; border: 1px solid #DDD; -moz-border-radius: 3px; border-radius: 3px; font-size: 0.8em; width: 30%; float: right;">";
                $output .= "Title: <span class="item"><span class="fn entry-title" style="font-size: 0.8em;font-weight: normal;">".$title."</span></span><br />";
                $output .= "Reviewed by <span class="reviewer">".$author."</span> on <span class="dtreviewed"> ".$date_only."<span class="value-title" title="".$date.""></span></span><br/>";
                $output .= "Rating: <span class="rating">".$rating."</span><br/>";
                $output .= ( 0 < strlen($summary) ) ? "Summary: <span class="summary">".$summary."</span><br/>" : "";
                $output .= ( 0 < strlen($description) ) ? "<p><span class="description">".$description."</span></p>" : "";
                $output .= "</div>";
            }

            $content = $output.$content ;
        }
    }
    return $content;
}
?>

if ($rating == "5.0"){
    print '<img src="stars/5-0.png">';
}