What is php's performance on directly accessing array's row with key specified -

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i have question regarding array's performance.... how php handle array keys? mean if $my_city = $cities[15]; .... php directly access exact row item in $cities array or php iterate trough array until finds matched row?

and if access row directly... there difference in performance between array 100 rows , array 100,000 rows?

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

php's arrays implemented hash tables, elements accessed directly possible, without iterating through everything. read more algorithm here: http://en.wikipedia.org/wiki/hash_table


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