Outside of the PHP interpreter, create a new template file in the style of Example 10-2. Use file_get_contents( ) and file_put_contents( ) to read an HTML template file, substitute values for the template variables, and save the new page to a separate file.

Outside of the PHP interpreter, create a file that contains some email addresses, one per line. Make sure a few of the addresses appear more than once in the file. Call that file addresses.txt. Then, write a PHP program that reads each line in addresses.txt and counts how many times each address appears. For each distinct address in addresses.txt, your program should write a line to another file, addresses-count.txt. Each line in addresses-count.txt should consist of the number of times an address appears in addresses.txt, a comma, and the email address. Write the lines to addresses-count.txt in sorted order from the address that occurs the most times in addresses.txt to the address that occurs the fewest times in addresses.txt.

Display a CSV file as an HTML table. If you don't have a CSV file (or spreadsheet program) handy, use the data from Example 10-10.

Write a PHP program that displays a form that asks a user for the name of a file underneath the web server's document root directory. If that file exists on the server, is readable, and is underneath the web server's document root directory, then display the contents of the file. For example, if the user enters article.html, display the file article.html in the document root directory. If the user enters catalog/show.php, display the file show.php in the directory catalog under the document root directory. Table 6-1 tells you how to find the web server's document root directory.

Modify your solution to the previous exercise so that the program displays only files whose names end in .html. Letting users look at the PHP source code of any page on your site can be dangerous if those pages have sensitive information in them such as database usernames and passwords.