How can I improve the script below to be able to add global template parts such as start and end of the page?

  <?php
    class simpleTemplate {
        var $variables;
        var $variables_callback;
        var $contents;
        var $preg;
        var $regexps;
        // Constructor, initialize default variables
        function simpleTemplate(){
            // default sub regexp matches
            $this->preg['var'] = '[a-zA-Z.\-_]{1,50}';

            //INSERT REGEXP

            $this->php_start = "\necho '";
            $this->php_end = "';\n";
            // Main find-replace regexps
            $this->regexps = array(
                // echo-variable statement: {(var)}
                'echo' => array(
                    'search' => '~\{((?:'.$this->preg['var'].')(?:\.)?)\}~sU',
                    'replace' => "'.\$this->_get('\\1').'"
                )
       'include' => array(
           'search' => '', // UPDATE
                    'replace' => "" // UPDATE
       )
            );
        }
        // Load a file and convert it into native PHP code
        function load($file){
            if (!is_readable($file))
                return FALSE;
            $this->file = $file;
            $this->contents = NULL;
            if (!isset($this->contents)){
                $this->contents = file_get_contents($this->file);
                $this->parse();
            }
        }
        // Load a converted template, apply variables and echo the output
        function show(){
            ob_start();
            eval($this->contents);
            ob_end_flush();
        }
        // Main converter, call sub-convertors and perform some cleaning
        function parse(){
            $this->contents = str_replace("'", "\'", $this->contents);
            $this->contents = $this->php_start.$this->contents.$this->php_end;
            foreach ($this->regexps as $regexp)
                do {
                    if (isset($contents))
                        $this->contents = $contents;
                    $contents = preg_replace($regexp['search'], $regexp['replace'], $this->contents);
                } while ($contents != $this->contents);
            $this->clean();
        }
        // Clean trash in generated PHP code
        function clean(){
            $this->contents = preg_replace("~([^\\\])''\.~", '\1', $this->contents);
            $this->contents = str_replace(".''", "", $this->contents);
            $this->contents = str_replace("\necho '';\n", "", $this->contents);
            $this->contents = str_replace("else {}", "", $this->contents);
            // Remove all whitespace from the template output
            //$this->contents = preg_replace("~(\s{2,}|\n)~", '', $this->contents);
            return;
        }
        // Get a variable from internal, or an external source
        function _get($variableName){
            $variable = @eval('return $this->variables[\''.str_replace('.', "']['", $variableName).'\'];');
            if (!isset($variable)) {
                if (isset($this->variables[$variableName]))
                    $variable = $this->variables[$variableName];
                else {
                    // Support for an external variable-source
                    $function_name = $this->variables_function;
                    if (isset($variables_callback))
                        $variable = call_user_func($variables_callback, $variableName);
                }
            }
            if (!isset($variable))
                return FALSE;
            else
                return $variable;
        }
        // Set an internal variable
        function _set($variableName, $value){
            $this->variables[$variableName] = $value;
            return TRUE;
        }
    }
    ?>

Örnek. Php sayfa benziyor

<?php
require_once('tpl.php');     
$tpl = new simpleTemplate();
$data['user'] = array(
        'name' => 'Denis',
        'surname' => 'Bobrovnikov'
);
$tpl->variables = $data;
$tpl->load('index.tpl');
$tpl->show();
?>

Ve şablon şudur

My name is {user.name} {user.surname}

Ben şablon dosyasında bunu mümkün olmak istiyorum

{include=header.tpl}
My name is {user.name} {user.surname}
{include=footer.tpl}

burada header ve footer da çözümlenir