PHP to save content from custom form fields in Wordpress.

Save Function

<?php
add_action( 'save_post', 'cd_meta_box_save' );
function cd_meta_box_save( $post_id )
{
  // Bail if we're doing an auto save
	if( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE ) return;
	
	// if our nonce isn't there, or we can't verify it, bail
	if( !isset( $_POST['meta_box_nonce'] ) || !wp_verify_nonce( $_POST['meta_box_nonce'], 'my_meta_box_nonce' ) ) return;
	
	// if our current user can't edit this post, bail
	if( !current_user_can( 'edit_post' ) ) return;
	
	// now we can actually save the data
	$allowed = array( 
		'a' => array( // on allow a tags
			'href' => array() // and those anchors can only have href attribute
		)
	);
	
	// Make sure your data is set before trying to save it
	if( isset( $_POST['my_meta_box_text'] ) )
		update_post_meta( $post_id, 'my_meta_box_text', wp_kses( $_POST['my_meta_box_text'], $allowed ) );
		
	if( isset( $_POST['my_meta_box_select'] ) )
		update_post_meta( $post_id, 'my_meta_box_select', esc_attr( $_POST['my_meta_box_select'] ) );
		
	// This is purely my personal preference for saving check-boxes
	$chk = isset( $_POST['my_meta_box_check'] ) && $_POST['my_meta_box_select'] ? 'on' : 'off';
	update_post_meta( $post_id, 'my_meta_box_check', $chk );
}
?>