PHP Anti-Patterns (PHP World 2014)

Most programming conferences these days have a talk on object-oriented design patterns. Everyone is happy to tell you how you SHOULD be writing code. In this talk we will cover how NOT to write PHP. I've scoured the internet for examples of common pitfalls for PHP developers from beginner to advanced. We'll take a lighthearted yet serious look at issues like security, performance, code style, quirks of the language, and more.

Transcript

1. PHP Anti Patterns (and how you’re guilty of using them) Josh Butts PHPWorld 2014
2. About Me • Over 10 years of “pro” PHP • VP of Engineering at Offers.com • Long-time Austin PHP organizer • Taught several PHP classes • I play competitive Skee Ball • github.com/jimbojsb @jimbojsb
3. Preface • This talk is 100% my opinion • You may disagree with some of it • I disagree with some of it • Find me after and tell me why I’m wrong • PHP is ever-changing. This talk could be wrong 6 months from now
4. What is an Anti-Pattern? An anti-pattern (or antipattern) is a common response to a recurring problem that is usually ineffective and risks being highly counterproductive. (so says Wikipedia)
5. What is an Anti-Pattern
6. What is an Anti-Pattern • Tend to appear in OOP • Contradict good OOP patterns • In PHP, there are plenty of non-ooo examples too • Why does the PHP let us do it then?
7. Everyone Is Guilty • Road to hell is paved with good intentions • Lesser of the evils • Good software design doesn’t (necessarily) make money • Blame PHP
8. NIH Syndrome • Everyone should write their own X • Don’t actually use it • Re-inventing an already documented bad idea
9. Singletons You might as well just use global variables
10. Examples • Public statics • Service locators • Bad DI Containers
11. Why would you use a singleton • Cross-cutting concerns • Configuration options • State-passing in a legacy system
12. Example Singleton Class <?php class Singleton { private static $instance; public static function getInstance() { if (!($instance instanceof self)) { self::$instance = new self(); } return self::$instance; } }
13. God Objects - The Worst Singletons Zend_Controller_Front • The core request handler for Zend Framework 1.x • Singleton with a public getInstance() method • Has a reference to EVERYTHING • Change the response code from your view • Disable exception handling from your models • Really, very, extremely convenient
14. Your First PHP Job
15. Your Second PHP Job
16. Database IPC Your database is not a job queue
17. Database IPC • We’ve all done this • Probably at your second PHP job • MySQL is your everything • But it’s easy and it works…
18. Database IPC • Sure, it works on your local dev laptop • I promise this will fail you in production • Why: Locking, polling, IO, query cache • MediaWiki
19. But I would never database IPC! I bet you would.
20. How do you fix it? • Use a message or job queue • There are a ton of good ones • Beanstalkd • RabbitMQ • Gearman • Kafka • Amazon SQS
21. Interface Bloat In reality, no one will build an alternate implementation
22. Interface Bloat - How it starts out • Step 1 - Write Code • Step 2 - Publish on Github • Step 3 - Tweet your new lib • Step 4 - Fame?
23. Interface Bloat • Why do you use interfaces • Who is the audience of your code • Is there a reason to extend what you wrote? • Slippery slope • Java Envy
24. Pheanstalk\Pheanstalk <?php namespace Pheanstalk; interface PheanstalkInterface { const DEFAULT_PORT = 11300; const DEFAULT_DELAY = 0; // no delay const DEFAULT_PRIORITY = 1024; // most urgent: 0, least urgent: 4294967295 const DEFAULT_TTR = 60; // 1 minute const DEFAULT_TUBE = 'default'; public function setConnection(Connection $connection); public function getConnection(); public function bury($job, $priority = self::DEFAULT_PRIORITY); public function delete($job); public function ignore($tube); public function kick($max); public function kickJob($job); public function listTubes(); public function listTubesWatched($askServer = false); public function listTubeUsed($askServer = false); public function pauseTube($tube, $delay); public function peek($jobId); public function peekReady($tube = null); public function peekDelayed($tube = null); public function peekBuried($tube = null); public function put($data, $priority = self::DEFAULT_PRIORITY, $delay = self::DEFAULT_DELAY, $ttr = self::DEFAULT_TTR); public function putInTube($tube, $data, $priority = self::DEFAULT_PRIORITY, $delay = self::DEFAULT_DELAY, $ttr = self::DEFAULT_TTR); public function release($job, $priority = self::DEFAULT_PRIORITY, $delay = self::DEFAULT_DELAY); public function reserve($timeout = null); public function reserveFromTube($tube, $timeout = null); public function statsJob($job); public function statsTube($tube); public function stats(); public function touch($job); public function useTube($tube); public function watch($tube); public function watchOnly($tube); }
26. Enough with OOP Lets talk about about plain old PHP
27. Mixed returns • Check your data models • Check your database • E_FATAL
28. Common DB Example <?php class DB { public function query($sql) { $results = mysql_query($sql); if ($results) { $data = array(); while ($row = mysql_fetch_assoc($results)) { $data[] = $row; } return $data; } return false; } }
29. Slightly better - return array() <?php class DB { public function query($sql) { $results = mysql_query($sql); if ($results) { $data = array(); while ($row = mysql_fetch_assoc($results)) { $data[] = $row; } return $data; } return array(); } }
30. Better still <?php class DB { public function query($sql) { $results = mysql_query($sql); if ($err = mysql_error()) { throw new \RuntimeException($err); } if ($results) { $data = array(); while ($row = mysql_fetch_assoc($results)) { $data[] = $row; } return $data; } return array(); } }
31. Extract Not even once…
32. This is just a bad idea all around <?php // index.php?page=1 $importantVariable = 1; extract($_GET); //$page == 1;
33. Error Handling Throw a damn exception!
34. trigger_error() • From hard to impossible to handle during runtime • Just use exceptions - we even have finally now • Still 17 occurrences of trigger_error() in the Wordpress codebase • 22 in Joomla • Surprisingly only 3 in Drupal 8, and the seem to be outside the core
35. Sequential Coupling Your objects require their methods to be called in a certain order
36. Sequential Coupling • Requires setters after constructors • Failure to inject dependencies • Requiring external state management • valid() to check state? • Poorly written API clients
37. Don’t abuse PHP’s goofy booleans You’ll be sorry way down the road
38. Rating Example <?php $rating = “0"; if ($rating) { echo "Product is rated: " . $rating; } else { //this one executes echo "Product has received no ratings"; }
39. Rating Example <?php $rating = "0.00"; if ($rating) { //this one executes echo "Product is rated: " . $rating; } else { echo "Product has received no ratings"; }
40. Quick Hits One bullet says it all
41. Quick Hits • Writing your own password hashing • Having more than one require call in your code • Writing your own ORM • Changing the memory_limit • Running PHP <5.5 • Making assumptions about “goodness” of built in language functions • @ • ?>
43. The Elusive While-Break I’ve only ever seen this once, so maybe it’s not a pattern…
44. <?php $shouldRun = true while ($shouldRun) { $obj->method1(); $obj->method2(); break; }
46. What I didn’t mention, on purpose • Not writing tests • Not using a framework • Not using goto • Mixing PHP and HTML
47. Questions / Discussion?
48. Feedback • https://joind.in/11880 • josh@joshbutts.com • @jimbojsb