Preferred method to store PHP arrays (json_encode vs serialize)

Asked 2009-04-29T20:09:43.560

672

I need to store a multi-dimensional associative array of data in a flat file for caching purposes. I might occasionally come across the need to convert it to JSON for use in my web app but the vast majority of the time I will be using the array directly in PHP.

Would it be more efficient to store the array as JSON or as a PHP serialized array in this text file? I've looked around and it seems that in the newest versions of PHP (5.3), json_decode is actually faster than unserialize.

I'm currently leaning towards storing the array as JSON as I feel its easier to read by a human if necessary, it can be used in both PHP and JavaScript with very little effort, and from what I've read, it might even be faster to decode (not sure about encoding, though).

Does anyone know of any pitfalls? Anyone have good benchmarks to show the performance benefits of either method?

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2 Answers

I made a small benchmark as well. My results were the same. But I need the decode performance. Where I noticed, like a few people above said as well, unserialize is faster than json_decode. unserialize takes roughly 60-70% of the json_decode time. So the conclusion is fairly simple: When you need performance in encoding, use json_encode, when you need performance when decoding, use unserialize. Because you can not merge the two functions you have to make a choise where you need more performance.

My benchmark in pseudo:

Define array $arr with a few random keys and values
for x < 100; x++; serialize and json_encode a array_rand of $arr
for y < 1000; y++; json_decode the json encoded string - calc time
for y < 1000; y++; unserialize the serialized string - calc time
echo the result which was faster

On avarage: unserialize won 96 times over 4 times the json_decode. With an avarage of roughly 1.5ms over 2.5ms.

answered 2012-11-12T10:18:39.947

Before you make your final decision, be aware that the JSON format is not safe for associative arrays - json_decode() will return them as objects instead:

$config = array(
    'Frodo'   => 'hobbit',
    'Gimli'   => 'dwarf',
    'Gandalf' => 'wizard',
    );
print_r($config);
print_r(json_decode(json_encode($config)));

Output is:

Array
(
    [Frodo] => hobbit
    [Gimli] => dwarf
    [Gandalf] => wizard
)
stdClass Object
(
    [Frodo] => hobbit
    [Gimli] => dwarf
    [Gandalf] => wizard
)

answered 2009-10-21T03:34:54.743

Preferred method to store PHP arrays (json_encode vs serialize)

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