APC缓存文件与缓存变量

Question

Say I have a file a.php which only contains a large array:

$client = array(
    "a" => 123,
    "b" => 124,
    ...
 );

APC caches the file a.php but what does that mean exactly? It caches the opcode for the assignment only? Does it actually cache the mapping itself? Or do I need to explicitly put that in the APC cache?

Thanks!

Answer 1

APC caches a PHP file in byte code. This is a faster intermediary between human readable code and what the interpreter ends up executing. This is analogous to compiling a C/C++ file into a binary. An array compiled in this fashion will load quicker than if you read it form file.

Accessing an element in an associative array in php is constant time O(1) in Big-O. Adding an element is also O(1). By and large its best to store such arrays in the database because it uses less memory and is much more flexible. Keep in mind that every browser that visits this application is going to have its own copy of this array, where as if you use a database there would be only one copy. For instance if you want to look up a key based on its value you'll have to iterate over it which is O(n) (which is slow), the use of a database will be much faster.