Populate Gravity Form with email from post meta and output contact form on front end if the post author fills it out.

gravity-form-with-post-meta

/**
 * Add Contact Meta Box to Posts, Pages, or Any Custom Post Type 
 * Adds a contact form to single post pages when filled out
 * Get the Gravity Forms plugin, then
 * put this is your functions file
 */
$contact_meta_box = array(
	'id' => 'jm-contact-meta-box',
	'title' => 'Contact Email',
	'context' => 'normal',
	'priority' => 'high',
	'fields' => array(
		array(
			'name' => 'Email',
			'id' => 'sh_post_email',
			'type' => 'text',
		)
	)
);
add_action('admin_menu', 'sh_contact_add_box');

// Add contact meta box to posts
function sh_contact_add_box() {
	global $contact_meta_box;
	add_meta_box($contact_meta_box['id'], $contact_meta_box['title'], 'show_sh_contact_box', 'page', $contact_meta_box['context'], $contact_meta_box['priority']);
	add_meta_box($contact_meta_box['id'], $contact_meta_box['title'], 'show_sh_contact_box', 'post', $contact_meta_box['context'], $contact_meta_box['priority']);
	
	add_meta_box($contact_meta_box['id'], $contact_meta_box['title'], 'show_sh_contact_box', 'add-your-custom-post-type-slug', $contact_meta_box['context'], $contact_meta_box['priority']); // repeat this line for each CPT you want this to work on
}
function show_sh_contact_box() {
	global $contact_meta_box, $post;	
	echo '<input type="hidden" name="sh_contact_box_nonce" value="', wp_create_nonce(basename(__FILE__)), '" />';
	echo '<table class="form-table">';
	foreach ($contact_meta_box['fields'] as $field) {
		$contact_meta = get_post_meta($post->ID, $field['id'], true);
		echo '<tr><input type="text" name="', $field['id'], '" id="', $field['id'], '" value="', $contact_meta ? $contact_meta : '', '" size="30" style="width:99%" /></tr>';
		if ( !isset( $_POST[$field['id']] ) && get_post_meta( $post->ID, $field['id'], true ) == '' ) {
			echo '<tr><td><span class="description">Enter an email address to add a contact form to this post</span></td></tr>';
		} else {
			echo '';
		}
	}
	echo '</table>';
}

add_action('save_post', 'save_sh_contact_info');
function save_sh_contact_info($post_id) {
	global $contact_meta_box;
	if (!isset($_POST['sh_contact_box_nonce']) || !wp_verify_nonce($_POST['sh_contact_box_nonce'], basename(__FILE__))) {
		return $post_id;
	}
	if (defined('DOING_AUTOSAVE') && DOING_AUTOSAVE) {
		return $post_id;
	}
	if ('page' == $_POST['post_type']) {
		if (!current_user_can('edit_page', $post_id)) {
			return $post_id;
		}
	} elseif (!current_user_can('edit_post', $post_id)) {
		return $post_id;
	}
	foreach ( $contact_meta_box['fields'] as $field ) {
		$old = get_post_meta( $post_id, $field['id'], true );
		$new = $_POST[$field['id']];
		if ( $new && $new != $old ) {
			update_post_meta( $post_id, $field['id'], $new );
		} elseif ( '' == $new && $old ) {
			delete_post_meta( $post_id, $field['id'], $old );
		}
	}
}

/**
 * Populate Gravity Form with email from post meta
 */
add_filter('gform_field_value_author_email', 'populate_post_author_email');
function populate_post_author_email($value){
    global $post;
    $author_email = get_post_meta($post->ID, 'sh_post_email', true);
    return $author_email;
}

/** 
Read this: 
http://www.gravityhelp.com/documentation/page/Using_Dynamic_Population
http://www.gravityhelp.com/documentation/page/Dynamically_Populating_the_Post_Author
Put the following in your single post template, it will output a contact form only if the post author includes an email address in the post.
<?php
$author_email = get_post_meta($post->ID, 'sh_post_email', true);
if ($author_email == '' || !$author_email) : // If email contact, then show the form ?>
<?php else : ?>
<div class="clrit bot-spc">
<?php gravity_form(<<< enter id number of the form you created with Gravity Forms >>>, $display_title=false, $display_description=false, $display_inactive=false, $field_values=null, $ajax=false, $tabindex); ?>
</div>
<?php endif;  // End if email contact, then show the form ?>
*/