# Performance

**Note:** template generation is usually a small fraction of application's runtime. Before worrying about template performance, use profiler (e.g. [XDebug](http://xdebug.org/) + [KCacheGrind](http://kcachegrind.sourceforge.net/html/Home.html)) to verify that you're not barking up the wrong tree.

## Opcode accelerator

The **most important** thing is to install PHP accelerator like [APC](http://pecl.php.net/package/APC). If you're concerned about speed, it's crazy not to use one.

### opcode caches vs memcached

PHPTAL caches compiled templates on disk. Using `memcached` for template cache **would be slower**. Opcode accelerators like APC have their own in-memory cache and — most important — they store PHP code as compiled opcodes.

PHP has no way of storing compiled code in `memcached`, so the only way to use `memcached` is to `eval()` read templates, and that is the slowest way to run PHP code. Just letting APC to cache on-disk files is the fastest option.

## Avoiding stat()

On every request PHPTAL also checks if source template has changed. You can [implement](SourceResolver) your own `SourceResolver` and `Source` classes to avoid file timestamp checks or to load TAL template sources in a different way.

If you want PHP not to touch disk at all, also disable `apc.stat` in `php.ini`.

**Note:** don't do this unless you absolutely need to. Disabling stat gives only tiny performance improvements, but without it PHP and PHPTAL won't notice when files are updated.

## Faster TAL

In templates expressions that have multiple path components (`foo/bar/baz`) require some extra run-time checks. You can change those expressions to use `php:` modifier (e.g. `php:foo.bar['baz']`), which is a little bit faster.

Instead of using same complex expression multiple times, use `tal:define` to 'cache' its value. Access to `tal:define`d variables is quick.

Use `phptal:cache` to cache parts of templates that are very costly to generate. Currently there's no support for integration of `phptal:cache` with `memcached`, but [it's planned](cache).