Martin Sikora was working on an application that used a large dataset (in an array) and found some interesting things in regards to PHP's resulting loading time and saving time in four different types of arrays.

Recently I was dealing with precessing and storing large arrays in PHP (around 100 000 items) and I found out some quiet surprising facts that are very useful in performance critical applications. [...] When I started looking for some benchmark I found article Cache a large array: JSON, serialize or var_export?. That is really good but I wanted to compare a few more things.

He tested with four different array types including associative with an integer value and numeric index with a string value at sizes of 10, 100, 1,000 and 10,000 items. He ran his tests with the json methods, serializing them and a var_export. There's graphs of his results for each included in the post with some interesting variations between the different array types.