Test performance and memory usage for SplObjectStorage and array.
php benchmarks/splobjectstorage-vs-array.php
SplObjectStorage test
Time to fill: 0.0241971016
Time to check: 0.0091929436
Memory usage: 10.11 mb
Array test
Time to fill: 0.0317029953
Time to check: 0.0137040615
Memory usage: 29.41 mb