Saving Multiple Custom Meta Boxes

Hi, I’m creating a simple plugin to handle all the CMS stuff (custom post types, taxonomies, metaboxes, etc) on a site redesign. For the sake of simplifying future maintenance, I’m keeping all the custom data configurations in a series of simple arrays. For example…

function custom_metaboxes_array(){
	return array(
		array(
			'name'=>'post_subtitle',
			'label'=>'Subtitle',
			'description'=>'A subtitle for the post',
			'post_type'=>'post',
			'type'=>'text',
		),
		array(
			'name'=>'post_lede',
			'label'=>'Lede',
			'description'=>'A short paragraph of teaser text',
			'post_type'=>'post',
			'type'=>'text',
		),
		// etc...
	);
}

Most everything is displaying and working fine, but I’m unable to save the custom meta boxes. Here’s the code I’m working with, based on the WP documentation…

<?php
// Helpers
function as_nonce($str){
	return $str.'_nonce';
}

function as_fieldname($str){
	return $str.'-meta';
}

function as_key($str){
	return '_'.$str;
}

// Register the Metaboxes
function custom_metaboxes() {

	$metaboxes=custom_metaboxes_array();
	foreach($metaboxes as $m){
		$context= ($m['type']=='checkbox') ? 'side' : 'normal';
		$priority= ($m['type']=='checkbox') ? 'default' : 'high';
		add_meta_box(
			as_fieldname($m['name']),
			__( $m['label'], 'eb_plugin_textdomain' ),
			'custom_metaboxes_callback',
			$m['post_type'],
			$context,
			$priority,
			array('metadata'=>$m)
		);
	}

}
add_action( 'add_meta_boxes', 'custom_metaboxes' );

// Build the Metabox Forms
function custom_metaboxes_callback( $post, $metabox ) {

	$m=$metabox['args']['metadata'];
	$nonce_name=as_nonce($m['name']);
	$fieldname=as_fieldname($m['name']);
	$description=$m['description'];
	$label=$m['label'];
	$box_type=$m['type'];
	$key=as_key($m['name']);

	wp_nonce_field( 'eb_plugin_meta_box', $nonce_name );

	$value = get_post_meta( $post->ID, $key , true );

    // Text
    if($box_type=='text'){
	    ?>
	    <div class="custom-metabox">
	        <label for="<?php echo $fieldname;?>" class="meta-row-title hidden"><?php _e( $label , 'eb_plugin_textdomain' )?></label>
	        <input style="min-width:20em;" type="text" name="<?php echo $fieldname;?>" id="<?php echo $fieldname;?>" value="<?php esc_attr($value);?>" />
	        <div class="description <?php echo $fieldname;?>"><em><?php echo $description?></em></div>
	    </div>
	    <?php
	// Textarea
	}elseif($box_type=='textarea'){
		?>
		<div class="custom-metabox">
		    <label for="<?php echo $fieldname;?>" class="hidden"><?php _e( $label , 'eb_plugin_textdomain' )?></label>
		    <textarea style="width:98%;min-height:4em;" name="<?php echo $fieldname;?>" id="<?php echo $fieldname;?>"> <?php esc_attr($value);?> </textarea>
		    <div class="description <?php echo $fieldname;?>"><em><?php echo $description;?></em></div>
		</div>
		<?php
	// Checkbox
	}elseif($box_type=='checkbox'){
		?>
		<div class="custom-metabox">
		    <span class="hidden"><?php _e( $label , 'eb_plugin_textdomain' )?></span>
		    <div class="row-content">
		        <label for="<?php echo $fieldname;?>">
		            <input type="checkbox" name="<?php echo $fieldname;?>" id="<?php echo $fieldname;?>" value="1" <?php checked( $value, '1' ); ?> />
		            <?php _e( $label , 'eb_plugin_textdomain' )?>
		        </label>
		    </div>
		    <div style="margin-top:.75em;" class="description <?php echo $fieldname;?>"><em><?php echo $description;?></em></div>
		</div>
		<?php

	}else{
		echo 'Oops! Something went wrong. Make sure the type listed in custom_metaboxes_array() is valid (text, texarea, checkbox, radio, select).';
	}
}

function custom_metaboxes_save( $post_id ) {

	global $post;

	$post_id=$post_id ? $post_id : $post->ID;

	$metaboxes=custom_metaboxes_array();
	foreach($metaboxes as $m){

		$nonce_name=as_nonce($m['name']);
		$fieldname=as_fieldname($m['name']);
		$description=$m['description'];
		$label=$m['label'];
		$box_type=$m['type'];
		$key=as_key($m['name']);

		// Check if our nonce is set.
		if ( ! isset( $_POST[$nonce_name] ) ) {
			return;
		}

		// Verify that the nonce is valid.
		if ( ! wp_verify_nonce( $_POST[$nonce_name], 'eb_plugin_meta_box' ) ) {
			return;
		}

		// If this is an autosave, our form has not been submitted, so we don't want to do anything.
		if ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE ) {
			return;
		}

		// Check the user's permissions.
		if ( isset( $_POST['post_type'] ) && 'page' == $_POST['post_type'] ) {

			if ( ! current_user_can( 'edit_page', $post_id ) ) {
				return;
			}

		} else {

			if ( ! current_user_can( 'edit_post', $post_id ) ) {
				return;
			}
		}

		/* OK, it's safe for us to save the data now. */

		// Make sure that it is set.
		if ( ! isset( $_POST[$fieldname] ) ) {
			return;
		}

		// Sanitize user input.
		$sanitized = sanitize_text_field( $_POST[$fieldname] );

		// Update the meta field in the database.
		update_post_meta( $post_id, $key , $sanitized );		

	}

}
add_action( 'save_post', 'custom_metaboxes_save' );

Not sure what I’m missing but any help would be greatly appreciated.

Cheers — Erin