Simple template Class

<?php
/**
A very very simple html template php class (built for php4)
Copyright (C) 2006 Alexandru Plugaru ( alexandru.plugaru[guess what is here]info.uaic.ro ) http://students.info.uaic.ro/~alexandru.plugaru

This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.

*/

/**
 * Usage example:
 * 
 * In php file:
 * 
 * $obj= new template("template.html", "header.html", "footer.html"); //assinging current template + header + footer
 * $obj->assign_vars(array("VAR1"=>$content_var1, "VAR2" => $content_var2)); // setting up vars
 * $obj->assign_templates(array("SOME_HTML_BLOCK" => "other_template.html")); // other templates that should replace descriptors in current template
 * $obj->parse(); // parsing everything
 * $html = $obj->fetch(); // fetching the output string
 * echo $html; 
 * 
 * OR Simply:
 * 
 * $obj->output(); // echo output string
 * 
 * In template.html :
 * 
 * ... content ...
 * {VAR1} - this will be replaced with $content_var1
 * {VAR2} - this will be replaced with $content_var2
 * {SOME_HTML_BLOCK} - this will be replaced with contens other_template.html
 * 
 */

class template{
	var $templates_path = TEMPLATES_PATH;	//Templates path
	var $header=HEADER;						//Header file (header.html)
	var $footer=FOOTER;						//Footer file (footer.html)
	var $current_template;
	var $start="{";
	var $end="}";
	
	var $template_string="";		// This variable contains all the HTML that is needed for output
	var $header_string="";			// This var contains string that will be outputed instead of the header
	var $header_pattern="{HEADER}";	// This is the header pattern... use it in your templates like {HEADER}
	var $footer_string="";			// This var contains string that will be outputed instead of the footer
	var $footer_pattern="{FOOTER}";	// This is the footer pattern... use it in your templates like {FOOTER}
	var $variables = array(); 		// Variables in templates
	var $templates=array(); 		// Template variables in templates
	
	/**
	 * Constructor with current template file(needed), header template(optional) and footer template(optional) as parameters 
	 *
	 * @param String $current_template
	 * @param String $header
	 * @param String $footer
	 */
	function template($current_template,$header="", $footer=""){
		if($header != ""){
			$this->header=$header; //Assigning the header file
		}
		// Verifing if header file exists
		if(!file_exists($this->templates_path . $this->header)){
				echo "Header file $this->header does not exist"; 
		}else {
			$this->header_string=$this->read_file($this->templates_path . $this->header); //loading the header
		}
		if(!empty($footer)){
			$this->footer=$footer;// Assigning the footer file
		}
		// Testing if footer exists	
		if(!file_exists($this->templates_path . $this->footer)){
			echo "Footer file $this->footer does not exist";
		}else {
			$this->footer_string=$this->read_file($this->templates_path . $this->footer);
		}
		// Testing if template file exists
		if(!file_exists($current_template)){
			$this->current_template=$current_template; //setting up the current template filename
			$this->template_string=$this->read_file($this->templates_path . $this->current_template); //loading the template
		}
	}
	/**
	 * Return string of the readed 
	 *
	 * @param String $file filename
	 * @return String
	 */
	function read_file($file){
		return file_get_contents($file);
	}
	/**
	 * Here we are assigning template vars that will be parsed later
	 * Example: 
	 * $obj->assign_vars(array("VAR1"=>$content_var1, "VAR2" => $content_var2, etc.)); 
	 * In template file you need to have {VAR1} and {VAR2} that will be replaced with $content_var1 and $content_var2
	 * 
	 * @param Array $variables
	 */
	function assign_vars($variables){
		if(is_array($variables)){
			foreach ($variables as $variable => $value){
				$this->variables[$this->start . $variable . $this->end]=$value; //Adding start and end strings
			}
		}else {
			echo "Error! Template variables are not an array! ";
		}
	}
	/**
	 * Here we are assigning template files.
	 * Example: 
	 * $obj->assign_template(array("SOME_HTML_BLOCK" => "some_template.html"));
	 * In template file you need to have {SOME_HTML_BLOCK} that will be replaced with some_template.html file
	 * Also works with multiple files
	 * 
	 * @param Array $templates
	 */
	function assign_templates($templates){
		if(is_array($templates)){
			foreach ($templates as $template_descriptor => $template_file){
				$this->templates[$this->start . $template_descriptor . $this->end]=$this->read_file($this->templates_path .$template_file);
			}
		}else {
			echo "Error! Templates variables are not an array! ";
		}
	}
	
	/**
	* This method parses templates array and variables array and outputs the contents in a replaced form (html).
	*/
	function parse (){
		$pattern="/\\$this->start\w+\\$this->end/"; //here we have the perl regexp needed for searching and replacing the contents
		// this loop replaces all the included templates with the contents of the included template
		foreach ($this->templates as $template_descriptor => $value){
			$this->template_string=str_replace($template_descriptor,$value,$this->template_string);
		}
		// Here we will replace the header and the footer in our template
		$this->template_string=str_replace($this->header_pattern,$this->header_string,$this->template_string);
		$this->template_string=str_replace($this->footer_pattern,$this->footer_string,$this->template_string);
		
		// This loop replaces all the variables defined with $this->assign_vars()
		foreach ($this->variables as $variable_descriptor => $value){
			$this->template_string=str_replace($variable_descriptor,$value,$this->template_string);
		}
	}
	/**
	 * Output via echo
	 */
	function output(){
		echo $this->template_string;
	}
	/**
	 * Returns outputed string
	 *
	 * @return String
	 */
	function fetch(){
		return $this->template_string;
	}
}
?>