PHP Arrays

PHP Arrays

• 1.
  PHP Arrays. The Good,the Bad and the Ugly. Mahesh Gattani
• 2.
  About Me ● ● ● ● Senior SoftwareEngineer at Lucid Software Inc. Bachelors degree from IIT Delhi, India in Computer Science. Interests: ○ Sports, not the adventure types. Cricket anyone? ○ Long Drives ○ Reading Follow me on ○ methinking.tumblr.com
• 3.
  What are arrays?
• 4.
  PHP arrays: Thegood. ● ● ● ● ● ● Exceptionally easy to use. No need to allocate memory. Indexed and associative at the same time. Different types of keys allows in the same instance. Ordered. ... PHP arrays are not arrays... They are... Ordered Hash Maps
• 5.
  PHP arrays: Thebad PHP arrays are bad because… ● Runtime ○ O(n*n) worst case ■ Why you ask? Because they are maps. More about this later. ○ Rehashing. ● Memory Usage ○ Whole different beast.
• 6.
  UGLY! Weird, huh!? Size: 8? NextFree: 6? Bucket2, Bucket4? ● Collisions!
• 7.
  Hashmaps and collisions PHPhash function ● ● Integers: Integer mod size Strings: Hash function DJBX33A PHP DOS Attack by super colliding arrays! Fixed in 5.3.9
• 8.
  What to do? Findyour use case. Ex: Judy array
• 9.
  PHP Interfaces ● ArrayAccess ○ Interface to provide accessing objects as arrays ● Iterator ○ Interface for external iterators or objects that can be iterated themselves internally. ● Countable ○ Classes implementing this can be used with count() function.
• 10.
  Example SQLiteDBArray A simple, inmemory, indexed array implementation in PHP using SQLiteDB https://github.com/maheshgattani/SQLiteDBArray
• 11.
  References ● ● ● ● https://sheriframadan.com/2012/10/a-closer-look-into-php-arrays/ http://nikic.github.io/2011/12/28/Supercolliding-a-PHP-array.html www.php.net https://github.com/maheshgattani
• 12.
  Thank you!
• 13.
  Lucidchart ● ● ● ● Building the nextgeneration of collaborative web applications. VC funded, high growth, profitable. Graduates from Harvard, MIT, Stanford Team has worked at Google, Amazon, Microsoft. https://www.lucidchart.com/jobs