update meta field value after

Question

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>
?>

Answer 1

You are not retrieving the saved value for $model.

$model = get_post_meta( $post_id, 'auction_model', true );

And you should be sanitizing the values upon retrieval, or at least before echoing them:

<?php echo sanitize_text_field( $model ); ?>

---

You could also check for the value before calling update_post_meta() upon form submission, unless you intended to run that every time this page is loaded. If nothing else, you can at least check if $_POST has a value:

if ( isset( $_POST['auction_model'] && ! empty( $_POST['auction_model'] ) ) {
    update_post_meta( $post_id, 'auction_model', sanitize_text_field( $_POST['auction_model'] ) );
}

You can also then delete meta if the form field is empty:

else { 
     delete_post_meta( $post_id, 'auction_model' );
}

---

You can read more on sanitizing and validating user input here.

And more on the three *_post_meta() functions mentioned above here:

update_post_meta()

delete_post_meta()

get_post_meta()