什么是使用指定键直接访问数组行的php的性能

Question

I have a question regarding array's performance.... how does php handle array keys? I mean if I do something like $my_city = $cities[15]; .... does php directly access the exact row item in $cities array or does php iterate trough array until it finds the matched row?

and if it access the row directly... is there a difference in performance between an array with 100 rows and array with 100,000 rows?

like in this example $my_city = $cities[15];

Answer 1

PHP's arrays are implemented as hash tables, so the elements are accessed as directly as possible, without iterating through everything. Read more about the algorithm here: http://en.wikipedia.org/wiki/Hash_table