Building a Template Parser Class with PHP, Part I - Defining the structure of the PHP class (
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Despite the fact that PHP4 doesn’t offer a full-featured object-oriented programming model, with a bit of good will it’s quite possible to create classes and manipulate them in a decent way for the purposes of any project. Fortunately, with the release of PHP5, Object Oriented Programming has been greatly enhanced, introducing object-oriented features such as destructors, exception handling, true public and private methods and properties, and so on.
Regarding our class, we’re going to create it in PHP4, but it may be easily adapted to work seamlessly in PHP5. Let’s not waste more time in preliminaries and set up the class’ basics. Here’s the initial definition:
<?php
class templateParser {
// member definition
var $output;
function templateParser(){
// constructor setting up class initialization
}
function parseTemplate(){
// code for parsing template files
}
function display(){
// code for displaying the finished parsed page
}
}
?>
As can be deduced from the listed code, the class will expose three main methods for parsing template files (including the constructor). Please notice that I’ve defined the class property "$output", which will store the code for the parsed page as it’s being generated. That’s the only property that we need. For now, the class is very simple.
The constructor will accept one parameter, the template file to be parsed. Therefore, before we go deeper into the template parser class code, it’s necessary to have a template file for processing.
I’ve chosen a typical three-column design, with a "header", "navbar", left and right columns, and "footer" sections. Also I decided to delimit the placeholders using braces, since they’re seemingly the most common characters used in template files; hopefully, they allow more compatibility with other possible template systems. Having defined the general guidelines, the template file would look similar to this:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html>
<head>
<title>{title}</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<link rel="stylesheet" type="text/css" href="style.css" />
</head>
<body>
<div id="header">{header}</div>
<div id="navbar">{navbar}</div>
<div id="leftcol">{leftcontent}</div>
<div id="content">{maincontent}</div>
<div id="rightcol">{rightcontent}</div>
<div id="footer">{footer}</div>
</body>
</html>
As you can see, the template is extremely simplistic. However, keep in mind that each placeholder might be replaced with more complex structures, either from static or dynamic files. Now we’re moving forward. Since we’ve already defined the template file, let’s add some functionality to the class constructor, which takes the template file as the unique parameter:
function templateParser($templateFile='default_template.htm'){
(file_exists($templateFile))?$this->output=
file_get_contents($templateFile):die('Error:Template file '_
.$templateFile.' not found');
}
Let’s explain the tasks performed by the constructor. First, the method checks for the existence of the template file passed as parameter. If the file is found, it grabs the file contents using the "file_get_contents()" PHP built-in function, assigning them to the private variable (in fact it’s a property) $output. Since sometimes is useful to specify default values for incoming parameters, I’ve assigned a default file for the template file. In this case, the default template file is "default_template.htm", but it might be overridden, only passing the name of the other file to the constructor. If no template file is found, I stop the script from executing, displaying an error message to the user.
Now, the best part is coming up. It’s time to have a look at the "parseTemplate()" method, which is the main engine of the class. Let’s define it in the following manner:
function parseTemplate($tags=array()){
if(count($tags)>0){
foreach($tags as $tag=>$data){
$data=(file_exists($data))?$this->parseFile($data):$data;
$this->output=str_replace('{'.$tag.'}',$data,$this->output);
}
}
else {
die('Error: No tags were provided for replacement');
}
}
The method accepts an incoming array as a parameter, which stores the data to be inserted into the template placeholders. In this case, I’ve specified again a default "$tag" array, for passing data. Then, the method checks to verify whether the incoming "$tags" array is not empty. If it is not, it iterates over each array element, checking whether the value is a file. If the value corresponds to a file, the method calls the "parseFile()" private method, that, as the name suggest, will parse any file passed as an argument, including files with dynamic content, returning the file contents and assigning them to the local variable $data.
Don’t worry; we’ll see this method in detail in a moment. Let’s go back to the current method. If the value is not a file, it’s directly assigned to the $data variable. Next, the placeholder replacement operation is performed over that $data variable, substituting the placeholders with the proper values, and finally assigning the result to $output. Don’t forget that inside the class we’re referencing any property or method belonging to that class with the prefix "$this".
As you can appreciate, this last section is the workhorse of the method, since it’s where the placeholders’ replacement really occurs. If no valid array parameters are supplied, then I kill the script with the usual die statement, displaying a message that indicates the error. I’m sure the code is pretty easy to follow.
Well, I feel a little more comfortable now, having explained the "parseTemplate()" method, because it’s really the main performer of the class. There are still a couple of methods to explain. So, let’s move on and take a look at them.
| | Discuss Building a Template Parser Class with PHP, Part I | | | | | | | Definitively, building a small template system is easy with PHP. Hopefully... | | | | | | True... the article showed how easy it is to create sucha sistem..howevere these... | | | | | | Since the class was introduced as a simple template parser, the addition of new... | | | | | | The only things I see an immediate need for are a way to handle repeating fields... | | | | | | Unfortunately, those possible additions are not implemented in part II. I only... | | | | | | While I appreciate your approach, I can see an issue. I understand what I want it... | | | | | | Hello friend,
I get your point about a template system. It's truly desirable... | | | | | | Yes, if I could only get the swedish characters å ä ö Å Ä Ö to be displayed... | | | | | |
According to your needs, you should include the charset ISO-8859-1 into the head... | | | | | | Thanks for the fast reply!! :-)
I added the meta-tag. And I also added some code,... | | | | | | I'm glad you found a solution for the problem.
Just one advice: whenever you can,... | | | | | | one comment: mixing html and php is not a problem!!! replacing <?= $var => by {$var}... | | | | | |
Thank you for pointing that nice article. Sure it's very valuable for any web... | | | | | | Wonderful simple looking template parser; Your explanation is very understandable,... | | | | | | Hi friend,
I'm glad you liked the article. Of course I've no problem sending some... | | | | | | I was wondering how you would use this template system when you want different... | | | | | | It's easy to create different pages with the same template file. This way, you're... | | | | | | It's easy to create different pages with the same template file. This way, you're... | | | | | | Im fairly new to PHP and only know the basics of it. Im not sure how this could be... | | | | | | Yes, I see your point. Here´s a possible solution.
First, perform your queries, and... | | | | | | Yes thats what I want to do but as you said.. build it into a variable for example... | | | | | | Hello, here's your solution:
// initialize your output... | | | | | | I´m really glad I´ve been monitoring this discussion. This while-loop is just what... | | | | | | Hey, I'm glad you found it useful for your needs.
Thank you for the kind words and... | | | | | | Just learning about classes. I tried to use your code, but it didn't work. I did a... | | | | | | Hello, I found the error in your code. You listed the following:
foreach($tags as... | | | | | | Stunning class first of all. Very clear, very helpful and very practical.
Now the... | | | | | | Thank you for giving your opinions about the class.
Regarding your question, it´s... | | | | | | Thanks for getting back, so swifthly too.
I agree that adding the conditionals to... | | | | | | Forgot to add:
The template is thus:
{header}
{login-box}
{leftbox} | | | | | | Thank you for the kind words.
I think this is what you're looking for:
First,... | | | | | | Perfect solution.
Thanks again.
Like many others it seems, I'd love to see a... | | | | | | Nice to hear it was the solution for your problem.
About Part III, I hope to find... | | | | | | All going really well. Then I added a template which includes:
if... | | | | | | Hello friend,
I hope this helps. In first place when we're talking about a... | | | | | | Damn. You've pretty much said what I was hoping you wouldn't -- that being that it... | | | | | | Oddly, I've just noticed that if I reinstantiate the class within the tpl-footer... | | | | | | I guess I found the error. I will try to keep it short, so spiders won't index much... | | | | | | No, sadly that's not the answer. I should have perhaps mentioned, the init.inc.php... | | | | | | hi everybody
how i can build my database by php parsing . i mean that i wanna... | | | | | | There are several ways to update your database, even in that given short time. One... | | | | | | Hi there could the author possibly email me at liamdawe@gmail.com and help me out a... | | | | | | Hello,
I've emailed you at the given address. Thanks! | | | | | | is it any way i can get info from mysql into a {something}? like:
'cat' => ... | | | | | | About your question, I think that the best way to include query resources is first... | | | | | | thank you!
now i have another problem :(
it works when i just print out 2 things... | | | | | | Generally, and depending on the configuration file, PHP access files by using the... | | | | | | Very nice class indeed, simple, basic and yet very powerfull!
However, i`m trying... | | | | | | Thanks for the comments on the class. Now, let's point to your... | | | | | | Thank you for the quick reaction, and also the good example.
I think I can match... | | | | | | You're welcome. I'm glad to know the answer was helpful.
Regards. | | | | | | i`ve extended the class with the option to parse {img}{/img} tags too, using the... | | | | | | Nice class improvement. Adding image-parsing capabilities to the class' logic is a... | | | | | | Another contribution for your nice class, the option to make hyperlinks out of tags,... | | | | | | Excellent implementation of regular expressions. Also, trough regexp, another... | | | | | | I wanted to be able to also parse functions and function arguments with the same... | | | | | | Thank you for commenting on my PHP Template parser class article. I see that you... | | | | | | Hello, I am trying to loop through a template file like so :
There is two... | | | | | | Thanks for the kind comments on my PHP article. In a case like this, where the... | | | | | | Great article and exactly what I needed for my project.
You could update the... | | | | | | Thanks for the comments. I wrote this article over 4 years ago and updating its... | | | | | | >>> Post your comment now! | | | | | |
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