Simple WordPress Template-API

tplapi.php

/**
 * Add some rewrite rules
 *
 * @return void
 */
function tplapi_add_rewrite_rule(){
    add_rewrite_rule( '^tplapi/(.*?)/?$','index.php?tplapi=$matches[1]', 'top' );
}

add_action( 'init', 'tplapi_add_rewrite_rule', 0 );

/**
 * Add some query vars
 *
 * @return void
 */
function tplapi_add_query_vars( $qvars ) {
  $qvars[] = 'tplapi';
  return $qvars;
}

add_filter( 'query_vars', 'tplapi_add_query_vars', 10, 1 );

/**
 * Load custom template
 * 
 * @author r.reimann <info@rene-reimann.de>
 * @param 
 */
function tplapi_load_template( $default_tpl_path ){
	global $wp_query;
	
    if( array_key_exists( 'tplapi', $wp_query->query ) ){
        
        $tpl = $wp_query->query['tplapi'];
        
        $tpl_path = str_replace( basename( $default_tpl_path ), $tpl.'.php', $default_tpl_path );
        
    	if( file_exists( $tpl_path ) )
    		return $tpl_path;
    }
    
    return $default_tpl_path;
	
}

add_filter( 'template_include', 'tplapi_load_template', 99 );

/**
 * Validat the last Modifikation of this File
 * on modification flush the rewrite rules
 *
 * @author r.reimann <info@rene-reimann.de>
 * @return void
 */
function tplapi_flush_rules() {
    
	$o 	= '__UNIQUEKEY__';
	$v	= filemtime( __FILE__ );
	$d 	= array( 'version' => 0, 'time' => time() );
	$r 	= wp_parse_args( get_option( $o, array() ), $d );


	if ( $r['version'] != $v ) { 

		flush_rewrite_rules();
	
		$a = array( 'version' => $v, 'time' => time() );
	
		if ( ! update_option( $o , $a ) )
			add_option( $o , $a );


	}

}	

add_action( 'init', 'tplapi_flush_rules' );