I am trying to update meta field value.every thing ok problem is that field value does not showing in filed after refreshing the page  .Fro example when I update name value then its does not showing in filed value after refreshing the page.

<?php  
     update_post_meta($post_id, 'auction_model', trim( $_POST['Product_model']));
     $year=get_post_meta($post_id , 'Product_Year',true );
<form id="wdm-add-auction-form" class="auction_settings_section_style" action="" method="POST">
<table>
<tr valign="top">
    <th scope="row">
        <label for="auction_model"><?php _e('Product Model', 'wdm-ultimate-auction');?></label>
    </th>
    <td>
        <input name="auction_model" type="text" id="auction_model" class="regular-text" value="<?php echo $model;?>"/>
    </td>
</tr>
</table>

</form>
?>

I am trying to update meta field value. Everything ok, problem is that field value does not showing in field after refreshing the page.

For example, when I update name value then its does not show in field value after refreshing the page.

<?php  
     update_post_meta($post_id, 'auction_model', trim( $_POST['Product_model']));
     $year=get_post_meta($post_id , 'Product_Year',true );
<form id="wdm-add-auction-form" class="auction_settings_section_style" action="" method="POST">
<table>
<tr valign="top">
    <th scope="row">
        <label for="auction_model"><?php _e('Product Model', 'wdm-ultimate-auction');?></label>
    </th>
    <td>
        <input name="auction_model" type="text" id="auction_model" class="regular-text" value="<?php echo $model;?>"/>
    </td>
</tr>
</table>

</form>
?>