1	Python in PHP: Internals Jon Parise <jon@php.net> 2002 International PHP Conference Frankfurt, Germany November 6, 2002
2	About This Session Some familiarity with PHP extensions is expected. Python knowledge is not required, but familiarity will be helpful.
3	About Me Bachelor of Science in Information Technology from the Rochester Institute of Technology Completing Masters of Entertainment Technology at Carnegie Mellon University Software engineer at Maxis on The Sims Online Long history of involvement with PHP, PEAR, and The Horde Project Co-author of Professional PHP4 Programming Long-time Pythonista!
4	Ground Rules Questions Ask for clarification at any time. Please save scope-expanding questions until the end. Pacing Ask me to slow down if I move too quickly. I’m from New Jersey.
5	Session Agenda Overview Extension architecture Type conversions Object handling PHP Python Module Next Steps Questions
6	Confessions
7	What Is The Python Extension? Embedded Python interpreter Interface handled by PHP extension Python-to-PHP object proxy Handles type conversions Exposes PHP environment to Python
8	PHP Extension Architecture
9	Python Extension Architecture
10	How It Happens PHP starts and initializes the Python extension. The Python extension initializes the Python interpreter. Python-related operations are performed in PHP. PHP shuts down the Python extension, which cleans up the Python interpreter.
11	Executing Python Code
12	Executing More Python Code
13	How It Works Extension initialization Python initialization Python code execution Extension shutdown Python shutdown PHP_MINIT_FUNCTION Py_Initialize() PyRun_SimpleString() PHP_MSHUTDOWN_FUNCTION Py_Finalize()
14	py_eval() Executes a string of Python code Uses PyRun_SimpleString() Only returns success or failure Always executes in the same Python environment
15	Calling Python Functions
16	py_call() Calls a function of a module Uses PyObject_CallObject() Implicitly imports the module Allows parameter passing Returns the result of the function call
17	PHP to Python Type Conversion PHP Boolean Long (Integer) Double (Float) String Null Python Integer Long Double String None
18	Python to PHP Type Conversion Python Integer Long Float String None PHP Long Long Double String NULL
19	Arrays, Sequences & Mappings PHP only has hashes, indexed by: Numbers: array(1, 2) Strings: array('one' => 1, 'two' => 2) Python has sequences: Tuples: (1, 2) Lists: [1, 2] And mappings: Dictionaries: {'one': 1, 'two': 2}
20	Array Conversions PHP arrays (hashes) are always converted to Python dictionaries. Results in no data loss.
21	Array Conversion Exceptions Arrays of arguments are always passed as a tuple. String keys are discarded.
22	Sequence Conversions Python tuples and lists are always converted to PHP arrays. The numerical indices are preserved.
23	Mapping Conversions Python dictionaries are always converted to PHP associative arrays. Keys will be converted to strings.
24	About Python Objects The Python extension proxies Python objects Python objects are represented as instances of a "python" class in PHP
25	Creating Python Objects Python objects are creating using the Python() object constructor
26	Manipulating Python Objects Python objects work like PHP objects
27	Python Class Internals
28	Storing Python Objects Once created, Python objects are stored in the engine symbol hash
29	Retrieving Python Objects Python objects are retrieved by their handle
30	Handling Method Calls If the method name is 'python': Import the requested module Construct a new Python object Register and return the new object Else: Retrieve the Python object handle Look for the requested method Call the method with any arguments Convert and return the result
31	The Case-Sensitivity Problem PHP converts all function and method calls to lowercase internally You type: $test->GetSomeValue() PHP sees: $test->getsomevalue() Python is case-sensitive, making it impossible to call any function or method with capital letters from PHP!
32	The Case-Sensitivity Solution Build a map of Python object methods!
33	Handling Object Attributes Both "get" and "set" operations call the same attribute handler Retrieve the requested Python object Find the named attribute Convert and return its value Note: No case-sensitivity hacks necessary here!
34	The PHP Python Module Allows access to the PHP environment from within the embedded Python environment Functionality is still very limited!
35	php.var() Implementation
36	Building the Python Extension
37	Next Steps Extending Python objects from PHP Exposing PHP objects to Python More namespace sharing Global and local variables Multiple Python interpreters Better threading support Fix bugs
38	Questions
39	References Presentation Slides http://www.csh.rit.edu/~jon/pres/ Python in PHP http://www.csh.rit.edu/~jon/projects/pip/ Python http://www.python.org/