With the fundamentals of PHP under your belt, it's time to begin building truly dynamic Web sites. Dynamic Web sites, as opposed to the static ones on which the Web was first built, are easier to maintain, are more responsive to users, and can alter their content in response to differing situations.
In this chapter, I'll be covering a hodgepodge of ideas, all used to create dynamic Web applications. These include incorporating external files, handling forms and form data in new ways, writing and using your own functions, using PHP's date() function, and sending email. What all of these concepts have in common is that more sophisticated Web applications almost always use them.
Including Multiple Files
To this point, every script in the book has consisted of a single file that contains all of the required HTML and PHP code. But as you develop more complex Web sites, you'll see that this methodology has many limitations. PHP can readily make use of external files, a capability that allows you to divide your scripts into their distinct parts. Frequently you will use external files to extract your HTML from your PHP or to separate out commonly used processes.
PHP has four functions for using external files: include(), include_once(), require(), and require_once(). To use them, your PHP script would have a line like
Using any one of these functions has the end result of taking all the content of the included file and dropping it in the parent script (the one calling the function) at that juncture. An important attribute of included files is that PHP will treat the included code as HTML (i.e., send it directly to the browser) unless it contains code within the PHP tags.
Previous versions of PHP had a different distinction between when you'd use include() and when you'd use require().Now the functions are exactly the same when working properly but behave differently when they fail. If an include() function doesn't work (it cannot include the file for some reason), a warning will be printed to the Web browser ( Figure 3.1 ), but the script will continue to run. If require() fails, an error is printed and the script is halted ( Figure 3.2 ).
Figure 3.1 Two failed include() calls.
Figure 3.2 The first failure of a require() function will print an error and terminate the execution of the script.
Both functions also have a *_once() version, which guarantees that the file in question is included only once regardless of how many times a script may (presumably inadvertently) attempt to include it.
In this first example, I'll use included files to separate my HTML formatting from my PHP code. Then, the rest of the examples in this chapter will be able to have the same appearance without the need to rewrite the HTML every time. The concept results in a template system, an easy way to make large applications consistent and manageable. The focus in these examples is on the PHP code itself; you should also read the sidebar on "Site Structure" so that you understand the organization scheme of the files, and if you have any questions about the CSS (Cascading Style Sheets) or (X)HTML used in the example, see the references in Appendix C, "Resources."
To included multiple files
- Design an HTML page in your text or WYSIWYG editor (
Script 3.1 The HTML template for this chapter's Web pages. Download the layout.css file it uses from the book's supporting Web site.
Figure 3.3 The HTML and CSS design as it appears in the Web browser (without using any PHP).
Note: in order to save space, the CSS file for this example (which controls the layout) is not included in the book. You can download the file through the book's supporting Web site (see the site's Extras page) or do without it (the template will still work, it just won't look as nice).
- Copy everything from the first line of the layout's source to just before the page-specific content and paste it in a new document (
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <head> <meta http-equiv="content-type"content="text/html;charset=iso-8859-1" /> <title>Welcome to this Site!</title> <style type="text/css" media="all">@import "./includes/layout.css";</style> </head> <body> <div id="wrapper"> <div id="content"> <div id="nav"> <h3>Menu</h3> <ul> <li class="navtop"><a href="index.php" title="Go to the Home Page">Home</a> </li> <li><a href="calculator php" title="Use the Sales Calculator">Calculator</a> </li> <li><a href="dateform.php" title="Check out the Date Form">Date Form</a></li> <li><a href="register.php" title="Register">Register</a></li> </ul> </div> <!-- Script 3.2 - header.html -->
Script 3.2 The initial HTML for each Web page will be stored in a header file.
- Change the page's title line to read
<title><?php echo $page_title; ?> </title>I'll want the page title (which appears at the top of the Web browser; see Figure 3.3) to be changeable on a page-by-page basis. To do so, I set this as a variable that will be printed out by PHP.
- Save the file as header.html. Included files can use just about any extension for the filename. Some programmers like to use .inc to indicate that a file is used as an include. In this case, you could also use.inc.html, which would indicate that it's both an include and an HTML file (to distinguish it from includes full of PHP code).
- Copy everything in the original template from the end of the page-specific content to the end of the page and paste it in a new file (
<!-- Script 3.3 - footer.html --> </div> <div id="footer"><p>© Copyright 2005 by Larry E. Ullman & DMCInsights, Inc.</p></div> </div> </body> </html>
Script 3.3 The concluding HTML for each Web page will be stored in this footer file.
- Save the file as footer.html.
- Create a new PHP document in your text editor (
<?php # Script 3.4 - index.php
Script 3.4 This script generates a complete Web page using a template stored in external files.
- Set the $page_title variable and include the HTML header.
$page_title = 'Welcome to this Site!'; include ('./includes/header.html');The $page_title will allow me to set a new title for each page that uses this template system. Since I establish the variable before I include the header file, the header file will have access to that variable. Remember that this include() line has the effect of dropping the contents of the included file into this page at this spot.
- Close the PHP tags and copy over the page-specific content from the template.
?> <h1 id="mainhead">Big Header</h1> <p>This is where you'll put the main page content. This content will differ for each page.</p> <p>This is where you'll put the main page content. This content will differ for each page.</p> <p>This is where you'll put the main page content. This content will differ for each page.</p> <p>This is where you'll put the main page content. This content will differ for each page.</p> <h2>Subheader</h2> <p>This is where you'll put the main page content. This content will differ for each page.</p> <p>This is where you'll put the main page content. This content will differ for each page.</p> <p>This is where you'll put the main page content. This content will differ for each page.</p> <p>This is where you'll put the main page content. This content will differ for each page.</p>This information could be sent to the browser using echo(), but since there's no dynamic content here, it'll be easier and more efficient to exit the PHP tags temporarily.
- Create a final PHP section and include the footer file.
<?php include ('./includes/footer.html'); ?>
- Save the file as index.php and upload to your Web server.
- Create an includes directory in the same folder as index.php. Then place header.html, footer.html, and layout.ccs (downloaded from www.DMCInsights.com/phpmysql2), into this includes directory.
- Test the template system by going to the index.php page in your Web browser (
Figure 3.4 Now the same layout (see Figure 3.3) has been created using external files in PHP.
- If desired, view the HTML source of the page (
Figure 3.5 The generated HTML source of the Web page should replicate the code in the original template (refer to Script 3.1).