What is a practical way to validate words efficiently in PHP?

[johnsmithsp]

I’m working on a small PHP application that needs to validate user-entered words against a predefined word list. The basic approach of loading the list and checking each submitted word works, but I’m wondering how experienced PHP developers would structure this if the list becomes fairly large and validation happens frequently.

For example, a spelling bee game needs to check whether submitted words are valid and may also need to determine whether a word contains only permitted letters. I’m considering approaches such as an associative array for fast lookups, a database table with an indexed column, or loading the word list into memory.

For a PHP application of this type, which approach would you recommend? At what size would you move away from a simple in-memory lookup, and are there any PHP-specific performance or memory considerations I should take into account?