Page 371 - Beginning PHP 5.3

Chapter 11: Working with Files and Directories
displayFileList( “Invalid filename - please try again” );
return;

}

Notice that the function uses a regular expression to strip all characters from the filename except letters,
digits, underscores, hyphens, and spaces. For security reasons it ’ s always good to restrict user input to a
set of known safe characters (without being too restrictive). You can find out more on regular
expressions in Chapter 18, and user input filtering and validation in Chapter 20.
Next the function appends a .txt extension to the end of the filename and sets the $filepath variable
to store the full path to the file:
$filename .= “.txt”;

$filepath = PATH_TO_FILES . “/$filename”;
The file path is then checked to make sure the file doesn ’ t already exist; if it does, the user is warned
and the file isn ’ t created:
if ( file_exists( $filepath ) ) {

displayFileList( “The file $filename already exists!” );
If the file doesn ’ t exist, it is created by calling file_put_contents() with an empty string for the file
contents. ( file_put_contents() automatically creates a file if it doesn ’ t already exist.) If file_put_
contents() returns exactly false (tested with the === operator), the file can ’ t be created and the script
exits with an error:

} else {
if ( file_put_contents( $filepath, “” ) === false ) die( “Couldn’t create

file” );
Once the file has been created its permissions are set so that anyone can read and write to the file. Finally,
displayEditForm() is called, passing in the name of the newly created file so the user can begin
editing it:

chmod( $filepath, 0666 );

displayEditForm( “$filename” );

The displayPageHeader () Function
The displayPageHeader() utility function simply outputs the XHTML page header common to all
pages in the application. This saves having to include the markup more than once in the script. As well
as including the standard common.css style sheet from Chapter 2, the header defines some extra CSS
rules to style any error messages and the file list table:

< link rel=”stylesheet” type=”text/css” href=”common.css” / >
< style type=”text/css” >
.error { background: #d33; color: white; padding: 0.2em; }

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