1. php
  2. php-src


php-src / TODO-5.1

Zend Engine
  - Look at making zend_constant value member be a zval* instead of zval. (Andi)
  - Add the patch for referring to existing .ini vars in .ini files. (Andrei)
  - Implement inheritance rules for type hints. (Marcus) 
  - Implement true/false/NULL as keywords (apply the patch). (Andi, Marcus)
  - Implement typehinting for arrays (apply the patch). (Andi, Marcus)
  - Find a keyword for the if-set-or operator (apply the patch). (Marcus, all)
  - Fix ZTS destruction (apply the patch). (Marcus)

Build System
  - Implement load order of built-in extensions (apply the patch). (Wez)

Standard Library
  - Implement new time/date parsing and handling functions. (Derick)