PHP Web Fundamentals
Program: Tiny Wiki
The program puts together various concepts and implements a complete wiki system—a website whose pages are all user-editable.It follows a structure common among simple PHP programs of its type. The first partof the code defines various configuration settings. Then comes an if/else section that decides what to do (display a page, save page edits, etc.) based on the values of submitted form or URL variables. The remainder of the program consists of the functions invoked from that if/else section—functions to print the page header and footer, load saved page contents, and display a page-editing form.
The Tiny Wiki relies on an external library, PHP Markdown by Michel Fortin, to handle translating from the handy and compact Markdown syntax to HTML.
The Tiny Wiki relies on an external library, PHP Markdown by Michel Fortin, to handle translating from the handy and compact Markdown syntax to HTML.
<?php
// Install PSR-0-compatible class autoloader
spl_autoload_register(function($class){
require preg_replace('{\\\\|_(?!.*\\\\)}', DIRECTORY_SEPARATOR,
trim($class, '\\')).'.php';
});
// Use Markdown for Wiki-like text markup
// Located at http://michelf.ca/projects/php-markdown/
use \Michelf\Markdown;
// The directory where the Wiki pages will be stored
// Make sure the web server user can write to it
define('PAGEDIR', dirname(__FILE__) . '/pages');
// Get page name, or use default
$page = isset($_GET['page']) ? $_GET['page'] : 'Home';
// Figure out what to do: display an edit form, save an
// edit form, or display a page
// Display an edit form that's been asked for
if (isset($_GET['edit'])) {
pageHeader($page);
edit($page);
pageFooter($page, false);
}
// Save a submitted edit form
else if (isset($_POST['edit'])) {
file_put_contents(pageToFile($_POST['page']), $_POST['contents']);
// Redirect to the regular view of the just-edited page
header('Location: http://'.$_SERVER['HTTP_HOST'] . $_SERVER['SCRIPT_NAME'] .
'?page='.urlencode($_POST['page']));
exit();
}
// Display a page
else {
pageHeader($page);
// If the page exists, display it and the footer with an "Edit" link
if (is_readable(pageToFile($page))) {
// Get the contents of the page from the file it's saved in
$text = file_get_contents(pageToFile($page));
// Convert Markdown syntax (using Markdown library loaded above)
$text = Markdown::defaultTransform($text);
// Make bare [links] link to other wiki pages
$text = wikiLinks($text);
// Display the page
echo $text;
// Display the footer
pageFooter($page, true);
}
// If the page doesn't exist, display an edit form
// and the footer without an "Edit" link
else {
edit($page, true);
pageFooter($page, false);
}
}
// The page header -- pretty simple, just the title and the usual HTML
// pleasantries
function pageheader($page) { ?>
<html>
<head>
<title>Wiki: <?php echo htmlentities($page) ?></title>
</head>
<body>
<h1><?php echo htmlentities($page) ?></h1>
<hr/>
<?php
}
// The page footer -- a "last modified" timestamp, an optional
// "Edit" link, and a link back to the front page of the Wiki
function pageFooter($page, $displayEditLink) {
$timestamp = @filemtime(pageToFile($page));
if ($timestamp) {
$lastModified = strftime('%c', $timestamp);
} else {
$lastModified = 'Never';
}
if ($displayEditLink) {
$editLink = ' - <a href="?page='.urlencode($page).'&edit=true">Edit</a>';
} else {
$editLink = '';
}
?>
<hr/>
<em>Last Modified: <?php echo $lastModified ?></em>
<?php echo $editLink ?> - <a href="<?php echo $_SERVER['SCRIPT_NAME'] >">Home</a>
</body>
</html>
<?php
}
// Display an edit form. If the page already exists, include its current
// contents in the form
function edit($page, $isNew = false) {
if ($isNew) {
$contents = '';
?>
<p><b>This page doesn't exist yet.</b> To create it, enter its contents below
and click the <b>Save</b> button.</p>
<?php } else {
$contents = file_get_contents(pageToFile($page));
}
?>
<form method='post' action='<?php echo htmlentities($_SERVER['SCRIPT_NAME']) ?>'>
<input type='hidden' name='edit' value='true'/>
<input type='hidden' name='page' value='<?php echo htmlentities($page) ?>'/>
<textarea name='contents' rows='20' cols='60'>
<?php echo htmlentities($contents) ?></textarea>
<br/>
<input type='submit' value='Save'/>
</form>
<?php
}
// Convert a submitted page to a filename. Using md5() prevents naughty
// characters in $page from causing security problems
function pageToFile($page) {
return PAGEDIR.'/'.md5($page);
}
// Turn text such as [something] in a page into an HTML link to the
// Wiki page "something"
function wikiLinks($page) {
if (preg_match_all('/\[([^\]]+?)\]/', $page, $matches, PREG_SET_ORDER)) {
foreach ($matches as $match) {
$page = str_replace($match[0], '<a href="'.$_SERVER['SCRIPT_NAME'].
'?page='.urlencode($match[1]).'">'.htmlentities($match[1]).'</a>', $page);
}
}
return $page;
}
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