Does PHP have a concept like a hash-table for in memory lookups? Can you store a single copy at the application level, so it's not bound to sessions? How difficult is it to raise and consume events across different classes or objects?

I'm thinking about a new server-based project, and Apache is a lot more common than IIS. A little cheaper, too, if you're having it hosted. So I'm wondering if PHP is well suited?

Just use an array for in memory lookups. There are no built in collection classes, so if you need keys that are non-strings or non-integers then you'll need to build it yourself.

Out of the box PHP provides no way to share data in memory between requests. You need some sort of PHP accelerator like APC or XCache.

As for events... Again, PHP provides no built-in functionality for this. The amount of built-in classes is very small. There are thousands of functions that do all sorts of things, but there aren't many actual library-like classes.

Instead, PHP has PEAR and PECL. The thought being that the developer will extend PHP with extensions from PECL or use libs from PEAR for whatever functionality he needs.

Anyway, I believe there is a PEAR package that offers some of the features you might find in other languages 'Observable'-type classes.

Hmmm. Sounds like there's a pretty steep learning curve. I might be better off with a language I already know...

But it sounds like you can use strings instead of integers to index arrays in PHP? How does that work? I know you could write a function to loop through the array until it finds a match, but is there a better method, out of the box?

Hmmm. Sounds like there's a pretty steep learning curve. I might be better off with a language I already know...

It depends. If you are used to the "Java way" for example, it might be a bit of a change to do it the "PHP way". In PHP things are usually a bit simpler. In Java for example you might get a File, and then a FileReader, and then decorate it BufferedReader etc etc. In PHP I think it's much more straight forward. PHP itself is a very simple language, but it might take some time to make the change.

If the project *needs* to run on as many hosts as possible then PHP is a great choice. But some things you describe, like shared memory between requests, need special software anyway.

But it sounds like you can use strings instead of integers to index arrays in PHP? How does that work? I know you could write a function to loop through the array until it finds a match, but is there a better method, out of the box?

In PHP arrays can be indexed by string or integer. And there is no difference between the two. Arrays are arrays, you can even mix integer keys with string keys. You can loop over arrays with a foreach construct.

Here's an example:

PHP Code:

$array = array(
    'hello' => 'world',
    0 => 'zero',
    'chroder' => 'member',
    99 => 'ninety nine'
);

foreach ($array as $key => $val) {
    echo "$key: $val\n";
}

// hello:world
// 0: zero
// etc 


See Arrays in the PHP manual for more examples and explanations.