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Michael Dowling:
Favor Hash Lookups Over Array Searches
March 21, 2014 @ 10:47:34

Michael Dowling has a recent post to his site comparing the performance of hash lookups versus array searches.

A common programming requirement is to match a string against a set of known strings. For example, let's say you were iterating over the words in a forum post and testing to see if a word is in a list of prohibited words. A common approach to this problem is to create an array of the known prohibited words and then use PHP's in_array() function to test if the string is found in the list. However, there's a simple optimization you can make to significantly improve the performance of the algorithm.

He includes two pieces of sample code - one showing the searching of an array using in_array and the other running an isset to locate a key. He points out that the in_array method is quite a bit slower than the hash (key) lookup and includes a benchmark script to prove it.The results are pretty clear, with the hash lookup coming in about 480% faster than the in_array. He also points out that as the size of the strings you're comparing grows, the performance of in_array drops even more.

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hash lookup search array inarray benchmark

Link: http://mtdowling.com/blog/2014/03/17/hash-lookups-over-array-search/

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