Phly, boy, phly
the weblog and site of Matthew Weier O'Phinney

Cgiapp 1.5 has been released; you may now download it.

This release fixes a subtle bug I hadn't encountered before; namely, when a method name or function name is passed as an argument to mode_param(), run() was receiving the requested run mode... and then attempting to process that as the mode param. The behaviour is now fixed, and is actually simpler than the previous (non-working) behaviour.

Also, on reading Chris Shiflet's paper on PHP security, I decided to reinstate the query() method. I had been using $_REQUEST to check for a run mode parameter; because this combines the GET, POST, and COOKIE arrays, it's considered a bit of a security risk. query() now creates a combined array of GET and POST variable (POST taking precedence over GET) and stores them in the property $_CGIAPP_REQUEST; it returns a reference to that property. run() uses that property to determine the run mode now.

Enjoy!

I've been playing with parameter testing in my various Cgiapp classes, and one test that seemed pretty slick was the following:

    if (!array_key_exists('some_string', $_REQUEST)) {
        // some error
    }

Seems pretty straight-forward: $_REQUEST is an associative array, and I want to test for the existence of a key in it. Sure, I could use isset(), but it seemed... ugly, and verbose, and a waste of keystrokes, particularly when I'm using the param() method:

    if (!isset($_REQUEST[$this->param('some_param')])) {
        // some error
    }

However, I ran into a pitfall: when it comes to array_key_exists(), $_REQUEST isn't exactly an array. I think what's going on is that $_REQUEST is actually a superset of several other arrays -- $_POST, $_GET, and $_COOKIE -- and isset() has some logic to descend amongst the various keys, while array_key_exists() can only work on a single level.

Whatever the explanation, I ended up reverting a bunch of code.

Inspired by a Slashdot book review of High Performance MySQL.

I've often suspected that I'm not a SQL guru... little things like being self taught and having virtually no resources for learning it. This has been confirmed to a large degree at work, where our DBA has taught me many tricks about databases: indexing, when to use DISTINCT, how and when to do JOINs, and the magic of TEMPORARY TABLEs. I now feel fairly competent, though far from being an expert -- I certainly don't know much about how to tune a server for MySQL, or tuning MySQL for performance.

Last year around this time, we needed to replace our MySQL server, and I got handed the job of getting the data from the old one onto the new. At the time, I looked into replication, and from there discovered about binary copies of a data store. I started using this as a way to backup data, instead of periodic mysqldumps.

One thing I've often wondered since: would replication be a good way to do backups? It seems like it would, but I haven't investigated. One post on the aforementioned Slashdot article addressed this, with the following summary:

1. Set up replication
2. Do a locked table backup on the slave

Concise and to the point. I only wish I had a spare server on which to implement it!

I've standardized my PHP programming to use the environment variable SCRIPT_NAME when I want my script to refer to itself in links and form actions. I've known that PHP_SELF has the same information, but I was more familiar with the name 'SCRIPT_NAME' from using it in perl, and liked the feel of it more as it seems to describe the resource better ('PHP_SELF' could stand for the path to the PHP executable if I were to go by the name only).

However, I just noticed a post on the php.general newsgroup where somebody asked what the difference was between them. Semantically, there isn't any; they should contain the same information. However, historically and technically speaking, there is. SCRIPT_NAME is defined in the CGI 1.1 specification, and is thus a standard. However, not all web servers actually implement it, and thus it isn't necessarily portable. PHP_SELF, on the other hand, is implemented directly by PHP, and as long as you're programming in PHP, will always be present.

Guess I have some grep and sed in my future as I change a bunch of scripts...

Occasionally, I've needed to process a lot of information from a script, but I don't want to worry about PHP timing out or the user aborting the script (by clicking on another link or closing the window). Initially, I investigated register_shutdown_function() for this; it will fire off a process once the page finishes loading. Unfortunately, the process is still a part of the current connection, so it can be aborted in the same way as any other script (i.e., by hitting stop, closing the browser, going to a new link, etc.).

However, there's another setting initialized via a function that can override this behaviour -- i.e., let the script continue running after the abort. This is ignore_user_abort(). By setting this to true, your script will continue running after the fact.

This sort of thing would be especially good for bulk uploads where the upload needs to be processed -- say, for instance, a group of images or email addresses.

In the past two days, I've seen two references to Practical PHP Programming, an online book that serves both as an introduction to programming with PHP5 and MySQL as well as a good advanced reference with many good tips.

This evening, I was browsing through the Performance chapter (chapter 18), and found a number of cool things, both for PHP and MySQL. Many were common sense things that I've been doing for awhile, but which I've also seen and shaken my head at in code I've seen from others (calculating loop invariables at every iteration, not using variables passed to a function, not returning a value from a function, not using a return value from a function). Others were new and gave me pause for thought (string concatenation with the '.' operator is expensive, especially when done more than once in an operation; echo can take a comma separated list).

Some PHP myths were also dispelled, some of which I've been wondering about for awhile. For instance, the amount of comments and whitespace in PHP are not a factor in performance (and PHP caching systems will often strip them out anyways); double quotes are not more expensive than single quotes unless variable interpolation occurs.

It also has some good advice for SQL optimization, and, more importantly, MySQL server optimization. For instance, the author suggests running 'OPTIMIZE TABLE table;' on any table that has been added/updated/deleted from to any large extent since creation; this will defrag the table and give it better performance. Use CHAR() versus VARCHAR(); VARCHAR() saves on space, but MySQL has to calculate how much space was used each time it queries in order to determine where the next field or record starts. However, if you have any variable length fields, you may as well use as many as you need -- or split off variable length fields (such as a TEXT() field) into a different table in order to speed up searching. When performing JOINs, compare on numeric fields instead of character fields, and always JOIN on rows that are indexed.

I haven't read the entire book, but glancing through the TOC, there are some potential downfalls to its content:

• It doesn't cover PhpDoc
• It doesn't appear to cover unit testing
• Limited coverage of templating solutions (though they are mentioned)
• Limited usage of PEAR. The author does mention PEAR a number of times, and often indicates that use of certain PEAR modules is preferable to using the corresponding low-level PHP calls (e.g., Mail and Mail_MIME, DB), but in the examples rarely uses them.
• PHP-HTML-PHP... The examples I browsed all created self-contained scripts that did all HTML output. While I can appreciate this to a degree, I'd still like to see a book that shows OOP development in PHP and which creates re-usable web components in doing so. For instance, instead of creating a message board script, create a message board class that can be called from anywhere with metadata specifying the database and templates to use.

All told, there's plenty of meat in this book -- I wish it were in dead tree format already so I could browse through it at my leisure, instead of in front of the computer.