Building a PHP Preprocessor with plain PHP

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What is a preprocessor? A preprocessor is a program that processes its input data to produce output that is used as input to another program.  http://en.wikipedia.org/wiki/Preprocessor

PHP: Hypertext Preprocessor

Preprocessor vs business logic

Preprocessor syntax basics  Simple syntax  Technically based on comments  Initiated by #-style  Limited set of directives  Common in other languages  C  C++  Lisp

Directives #define ➔ Setting a constan t ➔ Can be used for c onditionals

Directives #include ➔ Embed a file ➔ Works on source level ➔ No knowledge of ➔ Code structures ➔ Close/Open tags

Directives #if <condition> #elif <condition> ➔ Conditional ➔ Limited set of ope rations ➔ Standard conditio nals ➔ = != < > ...

Directives #ifdef #ifndef ➔ Conditional check for ➔ Constant being se t ➔ Constant not set

Directives #endif ➔ Close block after ➔ #if ➔ #elif ➔ #ifdef ➔ #ifndef ➔ #else

Still awake?

Still awake!

Preprocessor directives & PHP [theseer@rikka ~] cat testfile.php <?php #define foo "bar" #ifdef foo echo "hello!n"; #else echo "[else output]n"; #endif [theseer@rikka ~] cat testcode.php <?php require '../src/preprocessor.php'; $x = new TheSeerToolsPreProcessor(); $res = $x->processFile('testfile.php'); echo $res; [theseer@rikka ~] php testcode.php <?php echo “hello!n”;

The Preprocessor class

When to use a preprocessor  Platform specific  include / require  include_once / require_once  PHP Version compatibility  System dependet  ...

Require or Include..?

I/O in PHP  Every fileaccess is I/O  A file does not have to be local  External webserver (http, https)  File transfer (ftp, ssh/scp)  Archives (phar, tar, gz, bz2)  …  Almost all PHP I/O functions support streams

Streamwrapper in PHP  Allows for registration of custom protocols  C-based implementations  Userland implementations  Supports include and require  Compatible with bytecode caches

Creating a streamwrapper  Implement a stream class  Readonly or read-write?  File only or Directory support?  Register your class for your protocol  Avoid name clashes  You can unregister default protocols if need be  Do not mess with file://  Use the protocol

A Preprocessor stream  What we want  Run preprocessor on include/require  Should cache the result for reuse  Be transparent to the developer  DONE

Using the preprocessor stream [theseer@rikka ~] cat testfile.php <?php #define foo "bar" #ifdef foo echo "hello!n"; #else echo "[else output]n"; #endif [theseer@rikka ~] cat testcode2.php <?php require '../src/preprocessor.php'; require '../src/streamwrapper.php'; stream_wrapper_register('ppp', 'TheSeerToolsPreProcessorStream'); TheSeerToolsPreProcessorStream::setCachePath('/tmp'); include 'ppp://'.__DIR__.'/testfile.php'; [theseer@rikka ~] php testcode2.php Hello!

The Preprocessor stream class

Oh no...

Preprocessing What you get  Enhanced flexibility  New Issues  Code Coverage is off  Hidden dependencies will arise  Line numbers at runtime don't match source

Congrats!

Thank you!

Contact  Slides will be available: http://talks.thephp.cc  Preprocessor code: http://github.com/theseer  Please rate this talk: http://joind.in/1717  Contact options  Email: team@thePHP.cc / arne@thePHP.cc  Follow us on twitter:  @arneblankerts  @thephpcc

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Building a PHP Preprocessor with plain PHP

by Arne Blankerts on May 31, 2010

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Building a PHP Preprocessor with plain PHP — Presentation Transcript