Trying to add a custom meta box to wordpress - wordpress

Question

I am trying to add a custom meta box to a wordpress page which stores a value in a custom field. It is not working. The meta box is displayed but when you press update the value entered ito the text box is lost and nothing is written to the wp_postmeta table (no _c3m_sponsor_ur meta_key is created)
I have adapted this from an example online. I also tried adding a die statement to see if the save post is even called but nothing dies. I also dont understand why the add_post_meta isn't being created for the page
add_action( 'add_meta_boxes', 'c3m_sponsor_meta' );
function c3m_sponsor_meta() {
add_meta_box( 'c3m_meta', 'Sponsor URL Metabox', 'c3m_sponsor_url_meta', 'page', 'side', 'high' );
}
function c3m_sponsor_url_meta( $post ) {
$c3m_sponsor_url = get_post_meta( $post->ID, '_c3m_sponsor_url', true);
if (!isset($c3m_sponsor_url))
add_post_meta($post->ID, '_c3m_sponsor_url', '', false);
echo 'Please enter the sponsors website link below';
?>
<input type="text" name="c3m_sponsor_url" value="<?php echo esc_attr( $c3m_sponsor_url ); ?>" />
<?php
}
add_action( 'save_post', 'c3m_save_project_meta' );
function c3m_save_project_meta( $post_ID ) {
die('here');
global $post;
if( $post->post_type == "page" ) {
if (isset( $_POST ) ) {
update_post_meta( $post_ID, '_c3m_sponsor_url', strip_tags( $_POST['c3m_sponsor_url'] ) );
}
}
}
Any help in fixing this is muh appreciated
Thanks a lot

Answer 1

This may be help you:--
add_action( 'save_post', 'c3m_save_project_meta' );
function c3m_save_project_meta( $post_ID ) {
if ( isset( $_POST['post_type'] ) && 'page' == $_POST['post_type'] )
{
if (isset( $_POST ) ) {
update_post_meta( $post_ID, '_c3m_sponsor_url', strip_tags( $_POST['c3m_sponsor_url'] ) );
}
}
}
Edited:-
You can simply use Advanced Custom Fields plugin instead of using code. This plugin much helpful for custom meta fields.