Secure PHP Development- P18

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Secure PHP Development- P18: Welcome to Secure PHP Development: Building 50 Practical Applications. PHP has come a long way since its first incarnation as a Perl script. Now PHP is a powerful Web scripting language with object-oriented programming support. Slowly but steadily it has entered the non-Web scripting arena often reserved for Perl and other shell scripting languages. Arguably, PHP is one of the most popular Web platforms.

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56 Part I: Designing PHP Applications while(list($cmdID, $cmdName) = each($cmdArray)) { $cmdOptions .= “$cmdName”; } $template = new Template($TEMPLATE_DIR); $template->set_file(‘fh’, $MY_TEMPLATE); $template->set_block (‘fh’, ‘mainBlock’, ‘main’); $template->set_var(‘USERNAME’, $user); $template->set_var(‘CMD_OPTIONS’, $cmdOptions); $template->parse(‘main’,’mainBlock’, FALSE); $template->pparse(‘output’, ‘fh’); This example uses bad_screen.ihtml, shown in Listing 3-2, as the HTML interface file. A while loop is used to create $cmdOptions. Notice that some HTML tags are embedded in the following line: $cmdOptions .= “$cmdName”; This violates the principle of keeping all HTML out of the code. There are situations in which it isn’t possible to keep the HTML out, but in creating combo boxes you can. Listing 3-2: bad_screen.ihtml My Document Hello {USERNAME} {CMD_OPTIONS} Listing 3-3 shows a modified version of Listing 3-2. Here the combo box (select list) is shown as an embedded block called optionBlock within the mainBlock in the template. The {CMD_NAME} line is looped when the block is populated.
Chapter 3: PHP Best Practices 57 Listing 3-3: good_screen.ihtml My Document Hello {USERNAME} {CMD_NAME} To generate the combo box without having any HTML code inside the PHP application, we modify the last code segment as follows: $TEMPLATE_DIR = ‘/some/path’; $MY_TEMPLATE = ‘bad_screen.ihtml’; $cmdArray = array( ‘1’ => ‘Add’, ‘2’ => ‘Modify’, ‘3’ => ‘Delete’ ); $template = new Template($TEMPLATE_DIR); $template->set_file(‘fh’, $MY_TEMPLATE); $template->set_block (‘fh’, ‘mainBlock’, ‘main’); $template->set_block (‘mainBlock’, ‘optionBlock’, ‘options’); while(list($cmdID, $cmdName) = each($cmdArray)) { $template->set_var(‘CMD_ID’, $cmdID); $template->set_var(‘CMD_NAME’, $cmdName); $template->parse(‘options’,’optionBlock’, TRUE); }
58 Part I: Designing PHP Applications $template->set_var(‘USERNAME’, $user); $template->parse(‘main’,’mainBlock’, FALSE); $template->pparse(‘output’, ‘fh’); The embedded block optionBlock is populated using the while loop, which replaced the CMD_ID, and CMD_NAME inside the loop. The parse() method that is called to parse the optionBlock has the append flag set to TRUE. In other words, when the block is parsed, the output of the last parsed block is appended to the cur- rent one to make the list of options. Finally, the mainBlock is parsed as usual and the combo box is generated com- pletely from the interface template, without needing HTML tags in the PHP code. Reducing template code When using the Template object to display a user interface, you may think that many calls to the set_var() method are needed to replace template tags. For example: // OK - could be better $TEMPLATE_DIR = ‘/some/path’; $MY_TEMPLATE = ‘screen.ihtml’; $template = new Template($TEMPLATE_DIR); $template->set_file(‘fh’, $MY_TEMPLATE); $template->set_block (‘fh’, ‘mainBlock’, ‘main’); $template->set_var(‘FIRST’, $first); $template->set_var(‘LAST’, $last); $template->set_var(‘EMAIL’, $email); $template->set_var(‘AGE’, $age); $template->set_var(‘GENDER’, $gender); $template->parse(‘main’,’mainBlock’, false); $template->pparse(‘output’, ‘fh’); If you are assigning a lot of template variables to values like in the previous code segment, you can reduce the number of set_var() calls by combining all of the calls into a single call. This will speed up the application since a single call is faster than many calls to a method. An improved version of this script is shown below. // BETTER $TEMPLATE_DIR = ‘/some/path’; $MY_TEMPLATE = ‘screen.ihtml’;
Chapter 3: PHP Best Practices 59 $template = new Template($TEMPLATE_DIR); $template->set_file(‘fh’, $MY_TEMPLATE); $template->set_block (‘fh’, ‘mainBlock’, ‘main’); $template->set_var( array( ‘FIRST’ => $first, ‘LAST’ => $last, ‘EMAIL’ => $email, ‘AGE’ => $age, ‘GENDER’ => $gender ) ); $template->parse(‘main’,’mainBlock’, false); $template->pparse(‘output’, ‘fh’); In this example, a single instance of set_var() method is used to pass an unnamed associative array with template tags as keys and appropriate data as values. Best Practices for Documentation When you decide to develop software, you should create design and implementa- tion documentations. Design documentations include block diagrams that describe the system, flow charts that describe a specific process, class diagrams that show the class hierarchy, and so on. Implementation documentation also has flow charts to describe specific imple- mentation processes. Most importantly, though, you use inline code comments to describe what your code does. You can use single-line or multiple comments such as:
60 Part I: Designing PHP Applications All the code for this book is commented, although the inline code com- ments have been stripped out of the code listings printed in the book to reduce the number of lines and because the book covers each method in detail. However, you can get the commented version of the code on the accompanying CD-ROM and/or on the Web site for the book at www.evoknow.com/phpbook.php. Best Practices for Web Security In this section I will discuss a set of best practices that if practiced will result in bet- ter security for your Web applications. Keep authentication information away from prying eyes Many Web applications use authentication information to allow restricted access to the application using username/password or IP addresses. Similarly, all applica- tions using databases use database access information (host name, username/pass- word, port, etc.) that should never be revealed to any Web visitors. You should keep these authentication data away from prying eyes by using one of these methods: ◆ Store authentication data way from the Web document tree. Make your applications read authentication related files from outside the Web docu- ment tree so that these files are not browseable via Web. This will require that your Web server has read access to these files. No other user (other than the root) should have access to these files. ◆ If you cannot store authentication files outside your Web document tree for some reason, you need to make sure the authentication files are not browseable via the Web. This can be done by using file extensions and restricting these extensions from being served by the Web server. When using databases with applications always create a limited privilege user by following your database administration guide. This user should be allowed to only access the specific database that your application needs access to. You should never use a privileged database user account to access database from Web applications. Consult your database documentation for details on how to create limited privilege database users.