renaming bytecode to opcode

codeguy#462

_posts/14-02-01-Opcode-Cache.md

@@ -0,0 +1,25 @@
+---
+isChild: true
+anchor: opcode_cache
+---
+
+## Opcode Cache {#opcode_cache_title}
+
+When a PHP file is executed, under the hood it is first compiled to opcodes and, only then, the opcodes are executed.
+If a PHP file is not modified, the opcode will always be the same. This means that the compilation step is a waste of CPU resources.
+
+This is where opcode caches come in. They prevent redundant compilation by storing opcodes in memory and reusing it on successive calls.
+Setting up an opcode cache is a matter of minutes, and your application will speed up significantly. There's really no reason not to use it.
+
+As of PHP 5.5, there is a built-in opcode cache called [OPcache][opcache-book]. It is also available for earlier versions.
+
+Read more about opcode caches:
+
+* [OPcache][opcache-book] (built-in since PHP 5.5)
+* [APC](http://php.net/manual/en/book.apc.php) (PHP 5.4 and earlier)
+* [XCache](http://xcache.lighttpd.net/)
+* [Zend Optimizer+](http://www.zend.com/products/server/) (part of Zend Server package)
+* [WinCache](http://www.iis.net/download/wincacheforphp) (extension for MS Windows Server)
+* [list of PHP accelerators on Wikipedia](http://en.wikipedia.org/wiki/List_of_PHP_accelerators)
+
+[opcache-book]: http://php.net/manual/en/book.opcache.php