get all page templates

get-page-templates.php

<?php
	$post_templates = array();

	$theme = wp_get_theme();
	$files = (array) $theme->get_files( 'php', 1 );

	foreach ( $files as $file => $full_path ) {
		$headers = get_file_data( $full_path, array( 'Template Name' => 'Template Name' ) );
		if ( empty( $headers['Template Name'] ) ) {
			continue;
		}
		$post_templates[ $file ] = $headers['Template Name'];
	}
	echo '<pre>';
	print_r( $post_templates );
	echo '</pre>';