Preferred method to store PHP arrays json encode vs serialize

Question

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

User · Answer

JSON is simpler and faster than PHP s serialization format and should be used unless    You re storing deeply nested arrays  json decode     This function will return false if the JSON encoded data is deeper than 127 elements   You re storing objects that need to be unserialized as the correct class You re interacting with old PHP versions that don t support json decode

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Really nice topic and after reading the few answers  I want to share my experiments on the subject  I got a use case where some  quot huge quot  table needs to be queried almost every time I talk to the database  don t ask why  just a fact   The database caching system isn t appropriate as it ll not cache the different requests  so I though about php caching systems  I tried apcu but it didn t fit the needs  memory isn t enough reliable in this case  Next step was to cache into a file with serialization  Table has 14355 entries with 18 columns  those are my tests and stats on reading the serialized cache  JSON  As you all said  the major inconvenience with json encode json decode is that it transforms everything to an StdClass instance  or Object   If you need to loop it  transforming it to an array is what you ll probably do  and yes it s increasing the transformation time  average time  780 2 ms  memory use  41 5MB  cache file size  3 8MB  Msgpack  hutch mentions msgpack  Pretty website  Let s give it a try shall we   average time  497 ms  memory use  32MB  cache file size  2 8MB  That s better  but requires a new extension  compiling sometimes afraid people    IgBinary  GingerDog mentions igbinary  Note that I ve set the igbinary compact strings Offbecause I care more about reading performances than file size   average time  411 4 ms  memory use  36 75MB  cache file size  3 3MB  Better than msg pack  Still  this one requires compiling too  serialize unserialize  average time  477 2 ms  memory use  36 25MB  cache file size  5 9MB  Better performances than JSON  the bigger the array is  slower json decode is  but you already new that  Those external extensions are narrowing down the file size and seems great on paper  Numbers don t lie   What s the point of compiling an extension if you get almost the same results that you d have with a standard PHP function  We can also deduce that depending on your needs  you will choose something different than someone else   IgBinary is really nice and performs better than MsgPack Msgpack is better at compressing your datas  note that I didn t tried the igbinary compact string option   Don t want to compile  Use standards   That s it  another serialization methods comparison to help you choose the one   Tested with PHPUnit 3 7 31  php 5 5 10 - only decoding with a standard hardrive and old dual core CPU - average numbers on 10 same use case tests  your stats might be different

User · Answer

just an fyi -- if you want to serialize your data to something easy to read and understand like JSON but with more compression and higher performance  you should check out messagepack

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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      gt   hobbit        Gimli      gt   dwarf        Gandalf    gt   wizard          print r  config   print r json decode json encode  config       Output is   Array        Frodo    gt  hobbit      Gimli    gt  dwarf      Gandalf    gt  wizard   stdClass Object        Frodo    gt  hobbit      Gimli    gt  dwarf      Gandalf    gt  wizard

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I ve tested this very thoroughly on a fairly complex  mildly nested multi-hash with all kinds of data in it  string  NULL  integers   and serialize unserialize ended up much faster than json encode json decode   The only advantage json have in my tests was it s smaller  packed  size   These are done under PHP 5 3 3  let me know if you want more details   Here are tests results then the code to produce them  I can t provide the test data since it d reveal information that I can t let go out in the wild   JSON encoded in 2 23700618744 seconds PHP serialized in 1 3434419632 seconds JSON decoded in 4 0405561924 seconds PHP unserialized in 1 39393305779 seconds  serialized size   14549 json encode size   11520 serialize   was roughly 66 51  faster than json encode   unserialize   was roughly 189 87  faster than json decode   json encode   string was roughly 26 29  smaller than serialize        Time json encoding  start   microtime  true    for  i   0   i  lt  10000   i          json encode   test       jsonTime   microtime  true   -  start  echo  JSON encoded in  jsonTime seconds lt br gt         Time serialization  start   microtime  true    for  i   0   i  lt  10000   i          serialize   test       serializeTime   microtime  true   -  start  echo  PHP serialized in  serializeTime seconds lt br gt         Time json decoding  test2   json encode   test     start   microtime  true    for  i   0   i  lt  10000   i          json decode   test2       jsonDecodeTime   microtime  true   -  start  echo  JSON decoded in  jsonDecodeTime seconds lt br gt         Time deserialization  test2   serialize   test     start   microtime  true    for  i   0   i  lt  10000   i          unserialize   test2       unserializeTime   microtime  true   -  start  echo  PHP unserialized in  unserializeTime seconds lt br gt      jsonSize   strlen json encode   test      phpSize   strlen serialize   test      echo   lt p gt serialized size       strlen serialize   test        lt br gt    echo  json encode size       strlen json encode   test        lt br gt  lt  p gt         Compare them if    jsonTime  lt   serializeTime         echo  json encode   was roughly     number format    serializeTime    jsonTime - 1     100  2        faster than serialize       else if    serializeTime  lt   jsonTime         echo  serialize   was roughly     number format    jsonTime    serializeTime - 1     100  2        faster than json encode       else       echo  Unpossible          echo   lt BR gt         Compare them if    jsonDecodeTime  lt   unserializeTime         echo  json decode   was roughly     number format    unserializeTime    jsonDecodeTime - 1     100  2        faster than unserialize       else if    unserializeTime  lt   jsonDecodeTime         echo  unserialize   was roughly     number format    jsonDecodeTime    unserializeTime - 1     100  2        faster than json decode       else       echo  Unpossible          echo   lt BR gt        Compare them if    jsonSize  lt   phpSize         echo  json encode   string was roughly     number format    phpSize    jsonSize - 1     100  2        smaller than serialize       else if    phpSize  lt   jsonSize         echo  serialize   string was roughly     number format    jsonSize    phpSize - 1     100  2        smaller than json encode       else       echo  Unpossible

User · Answer

Depends on your priorities   If performance is your absolute driving characteristic  then by all means use the fastest one   Just make sure you have a full understanding of the differences before you make a choice   Unlike serialize   you need to add extra parameter to keep UTF-8 characters untouched  json encode  array  JSON UNESCAPED UNICODE    otherwise it converts UTF-8 characters to Unicode escape sequences   JSON will have no memory of what the object s original class was  they are always restored as instances of stdClass   You can t leverage   sleep   and   wakeup   with JSON By default  only public properties are serialized with JSON   in PHP gt  5 4 you can implement JsonSerializable to change this behavior   JSON is more portable   And there s probably a few other differences I can t think of at the moment   A simple speed test to compare the two   lt  php  ini set  display errors   1   error reporting E ALL       Make a big  honkin test array    You may need to adjust this depth to avoid memory limit errors  testArray   fillArray 0  5       Time json encoding  start   microtime true   json encode  testArray    jsonTime   microtime true  -  start  echo  JSON encoded in  jsonTime seconds n       Time serialization  start   microtime true   serialize  testArray    serializeTime   microtime true  -  start  echo  PHP serialized in  serializeTime seconds n       Compare them if   jsonTime  lt   serializeTime        printf  json encode   was roughly  01 2f   faster than serialize   n     serializeTime    jsonTime - 1    100     else if   serializeTime  lt   jsonTime         printf  serialize   was roughly  01 2f   faster than json encode   n     jsonTime    serializeTime - 1    100     else       echo  Impossible  n      function fillArray   depth   max         static  seed      if  is null  seed              seed   array  a   2   c   4   e   6   g   8   i   10             if   depth  lt   max             node   array            foreach   seed as  key                 node  key    fillArray  depth   1   max                     return  node            return  empty

User · Answer

I would suggest you to use Super Cache  which is a file cache mechanism which won t use json encode or serialize  It is simple to use and really fast compared to other PHP Cache mechanism    https   packagist org packages smart-php super-cache  Ex     lt  php require   DIR     vendor autoload php   use SuperCache SuperCache as sCache     Saving cache value with a key    sCache  cache   lt key gt   - gt set   lt value gt     sCache  cache  myKey  - gt set  Key value       Retrieving cache value with a key echo sCache  cache  myKey  - gt get      gt

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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  lt  100  x    serialize and json encode a array rand of  arr for y  lt  1000  y    json decode the json encoded string - calc time for y  lt  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

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I ve written a blogpost about this subject   quot Cache a large array  JSON  serialize or var export  quot   In this post it is shown that serialize is the best choice for small to large sized arrays  For very large arrays   gt  70MB  JSON is the better choice

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If to summ up what people say here  json decode encode seems faster than serialize unserialize BUT If you do var dump the type of the serialized object is changed  If for some reason you want to keep the type  go with serialize    try for example stdClass vs array   serialize unserialize   Array cache  array  size 2     a    gt  string  1   length 1     b    gt  int 2 Object cache  object stdClass  8    public  field1    gt  int 123 This cache  object Controller Test  8    protected  view    gt     json encode decode  Array cache  object stdClass  7    public  a    gt  string  1   length 1    public  b    gt  int 2 Object cache  object stdClass  8    public  field1    gt  int 123 This cache  object stdClass  8    As you can see the json encode decode converts all to stdClass  which is not that good  object info lost    So decide based on needs  especially if it is not only arrays

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First  I changed the script to do some more benchmarking  and also do 1000 runs instead of just 1     lt  php  ini set  display errors   1   error reporting E ALL       Make a big  honkin test array    You may need to adjust this depth to avoid memory limit errors  testArray   fillArray 0  5     totalJsonTime   0   totalSerializeTime   0   totalJsonWins   0   for   i   0   i  lt  1000   i             Time json encoding      start   microtime true        json   json encode  testArray        jsonTime   microtime true  -  start       totalJsonTime     jsonTime          Time serialization      start   microtime true        serial   serialize  testArray        serializeTime   microtime true  -  start       totalSerializeTime     serializeTime       if   jsonTime  lt   serializeTime             totalJsonWins              totalSerializeWins   1000 -  totalJsonWins      Compare them if   totalJsonTime  lt   totalSerializeTime        printf  json encode    wins   totalJsonWins  was roughly  01 2f   faster than serialize   n     totalSerializeTime    totalJsonTime - 1    100     else       printf  serialize    wins   totalSerializeWins  was roughly  01 2f   faster than json encode   n     totalJsonTime    totalSerializeTime - 1    100       totalJsonTime   0   totalJson2Time   0   totalSerializeTime   0   totalJsonWins   0   for   i   0   i  lt  1000   i             Time json decoding      start   microtime true        orig   json decode  json  true        jsonTime   microtime true  -  start       totalJsonTime     jsonTime        start   microtime true        origObj   json decode  json        jsonTime2   microtime true  -  start       totalJson2Time     jsonTime2          Time serialization      start   microtime true        unserial   unserialize  serial        serializeTime   microtime true  -  start       totalSerializeTime     serializeTime       if   jsonTime  lt   serializeTime             totalJsonWins              totalSerializeWins   1000 -  totalJsonWins       Compare them if   totalJsonTime  lt   totalSerializeTime        printf  json decode   was roughly  01 2f   faster than unserialize   n     totalSerializeTime    totalJsonTime - 1    100     else       printf  unserialize    wins   totalSerializeWins  was roughly  01 2f   faster than json decode   n     totalJsonTime    totalSerializeTime - 1    100         Compare them if   totalJson2Time  lt   totalSerializeTime        printf  json decode   was roughly  01 2f   faster than unserialize   n     totalSerializeTime    totalJson2Time - 1    100     else       printf  unserialize    wins   totalSerializeWins  was roughly  01 2f   faster than array json decode   n     totalJson2Time    totalSerializeTime - 1    100      function fillArray   depth   max         static  seed      if  is null  seed              seed   array  a   2   c   4   e   6   g   8   i   10             if   depth  lt   max             node   array            foreach   seed as  key                 node  key    fillArray  depth   1   max                     return  node            return  empty       I used this build of PHP 7      PHP 7 0 14  cli   built  Jan 18 2017 19 13 23    NTS   Copyright  c    1997-2016 The PHP Group Zend Engine v3 0 0  Copyright  c  1998-2016   Zend Technologies       with Zend OPcache v7 0 14  Copyright  c  1999-2016  by Zend Technologies   And my results were      serialize    wins  999  was roughly 10 98  faster than json encode     unserialize    wins  987  was roughly 33 26  faster than json decode     unserialize    wins  987  was roughly 48 35  faster than array   json decode     So clearly  serialize unserialize is the fastest method  while json encode decode is the most portable   If you consider a scenario where you read write serialized data 10x or more often than you need to send to or receive from a non-PHP system  you are STILL better off to use serialize unserialize and have it json encode or json decode prior to serialization in terms of time

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You might also be interested in https   github com phadej igbinary - which provides a  different serialization  engine  for PHP   My random arbitrary  performance  figures  using PHP 5 3 5 on a 64bit platform show    JSON     JSON encoded in 2 180496931076 seconds JSON decoded in 9 8368630409241 seconds serialized  String  size   13993   Native PHP     PHP serialized   in 2 9125759601593 seconds PHP unserialized in 6 4348418712616 seconds serialized  String  size   20769   Igbinary     WIN igbinary serialized    in 1 6099879741669 seconds WIN igbinrary unserialized in 4 7737920284271 seconds WIN serialized  String  Size   4467   So  it s quicker to igbinary serialize   and igbinary unserialize   and uses less disk space   I used the fillArray 0  3  code as above  but made the array keys longer strings   igbinary can store the same data types as PHP s native serialize can  So no problem with objects etc  and you can tell PHP5 3 to use it for session handling if you so wish   See also http   ilia ws files zendcon 2010 hidden features pdf - specifically slides 14 15 16

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I know this is late but the answers are pretty old  I thought my benchmarks might help as I have just tested in PHP 7 4 Serialize Unserialize is much faster than JSON  takes less memory and space  and wins outright in PHP 7 4 but I am not sure my test is the most efficient or the best  I have basically created a PHP file which returns an array which I encoded  serialised  then decoded and unserialised   array   include   DIR        tests data dao testfiles testArray php      JSON ENCODE  json encode memory start   memory get usage     json encode time start   microtime true    for   i 0   i  lt  20000   i            encoded   json encode  array       json encode time end   microtime true    json encode memory end   memory get usage     json encode time    json encode time end -  json encode time start   json encode memory     json encode memory end -  json encode memory start      SERIALIZE  serialize memory start   memory get usage     serialize time start   microtime true    for   i 0   i  lt  20000   i            serialized   serialize  array       serialize time end   microtime true    serialize memory end   memory get usage     serialize time    serialize time end -  serialize time start   serialize memory    serialize memory end -  serialize memory start      Write to file time   fpc memory start   memory get usage     fpc time start   microtime true    for   i 0   i  lt  20000   i            fpc bytes        file put contents            DIR        tests data dao testOneBigFile             lt  php return   var export  array true      gt               fpc time end   microtime true    fpc memory end   memory get usage     fpc time    fpc time end -  fpc time start   fpc memory    fpc memory end -  fpc memory start      JSON DECODE  json decode memory start   memory get usage     json decode time start   microtime true    for   i 0   i  lt  20000   i            decoded   json encode  encoded       json decode time end   microtime true    json decode memory end   memory get usage     json decode time    json decode time end -  json decode time start   json decode memory     json decode memory end -  json decode memory start      UNSERIALIZE  unserialize memory start   memory get usage     unserialize time start   microtime true    for   i 0   i  lt  20000   i            unserialized   unserialize  serialized       unserialize time end   microtime true    unserialize memory end   memory get usage     unserialize time    unserialize time end -  unserialize time start   unserialize memory     unserialize memory end -  unserialize memory start      GET FROM VAR EXPORT   var export memory start   memory get usage     var export time start   microtime true    for   i 0   i  lt  20000   i            array   include   DIR        tests data dao testOneBigFile       var export time end   microtime true    var export memory end   memory get usage     var export time    var export time end -  var export time start   var export memory    var export memory end -  var export memory start   Results  Var Export length  11447 Serialized length  11541 Json encoded length  11895 file put contents Bytes  11464 Json Encode Time  1 9197590351105 Serialize Time  0 160325050354 FPC Time  6 2793469429016 Json Encode Memory  12288 Serialize Memory  12288 FPC Memory  0 JSON Decoded time  1 7493588924408 UnSerialize Time  0 19309520721436 Var Export and Include  3 1974139213562 JSON Decoded memory  16384 UnSerialize Memory  14360 Var Export and Include  192

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THX - for this benchmark code   My results on array I use for configuration are as fallows  JSON encoded in 0 0031511783599854 seconds PHP serialized in 0 0037961006164551 seconds json encode   was roughly 20 47  faster than serialize   JSON encoded in 0 0070841312408447 seconds PHP serialized in 0 0035839080810547 seconds unserialize   was roughly 97 66  faster than json encode    So - test it on your own data

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Y just tested serialized and json encode and decode  plus the size it will take the string stored   JSON encoded in 0 067085981369 seconds  Size  1277772  PHP serialized in 0 12110209465 seconds  Size  1955548  JSON decode in 0 22470498085 seconds PHP serialized in 0 211947917938 seconds json encode   was roughly 80 52  faster than serialize   unserialize   was roughly 6 02  faster than json decode   JSON string was roughly 53 04  smaller than Serialized string   We can conclude that JSON encodes faster and results a smaller string  but unserialize is faster to decode the string

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I augmented the test to include unserialization performance  Here are the numbers I got   Serialize  JSON encoded in 2 5738489627838 seconds PHP serialized in 5 2861361503601 seconds Serialize  json encode   was roughly 105 38  faster than serialize     Unserialize  JSON decode in 10 915472984314 seconds PHP unserialized in 7 6223039627075 seconds Unserialize  unserialize   was roughly 43 20  faster than json decode      So json seems to be faster for encoding but slow in decoding   So it could depend upon your application and what you expect to do the most

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Check out the results here  sorry for the hack putting the PHP code in the JS code box    http   jsfiddle net newms87 h3b0a0ha embedded result   RESULTS  serialize   and unserialize   are both significantly faster in PHP 5 4 on arrays of varying size   I made a test script on real world data for comparing json encode vs serialize and json decode vs unserialize  The test was run on the caching system of an in production e-commerce site  It simply takes the data already in the cache  and tests the times to encode   decode  or serialize   unserialize  all the data and I put it in an easy to see table   I ran this on PHP 5 4 shared hosting server   The results were very conclusive that for these large to small data sets serialize and unserialize were the clear winners  In particular for my use case  the json decode and unserialize are the most important for the caching system  Unserialize was almost an ubiquitous winner here  It was typically 2 to 4 times  sometimes 6 or 7 times  as fast as json decode   It is interesting to note the difference in results from  peter-bailey   Here is the PHP code used to generate the results    lt  php  ini set  display errors   1   error reporting E ALL    function  count depth  array         count       0       max depth   0      foreach   array as  a            if  is array  a                 list  cnt   depth     count depth  a                count     cnt               max depth   max  max depth   depth             else                count                         return array           count           max depth   1            function run test  file         memory       memory get usage         test array   unserialize file get contents  file         memory       round  memory get usage   -  memory    1024  2        if  empty  test array      is array  test array             return             list  count   depth     count depth  test array          JSON encode test      start              microtime true        json encoded       json encode  test array        json encode time   microtime true  -  start         JSON decode test      start   microtime true       json decode  json encoded        json decode time   microtime true  -  start         serialize test      start            microtime true        serialized       serialize  test array        serialize time   microtime true  -  start         unserialize test      start   microtime true       unserialize  serialized        unserialize time   microtime true  -  start       return array           Name                      gt  basename  file            json encode   Time  s     gt   json encode time           json decode   Time  s     gt   json decode time           serialize   Time  s       gt   serialize time           unserialize   Time  s     gt   unserialize time           Elements                  gt   count           Memory  KB                gt   memory           Max Depth                 gt   depth           json encode   Win         gt    json encode time  gt  0  amp  amp   json encode time  lt   serialize time    number format   serialize time    json encode time - 1    100  2                 serialize   Win           gt    serialize time  gt  0  amp  amp   serialize time  lt   json encode time    number format   json encode time    serialize time - 1    100  2                 json decode   Win         gt    json decode time  gt  0  amp  amp   json decode time  lt   serialize time    number format   serialize time    json decode time - 1    100  2                 unserialize   Win         gt    unserialize time  gt  0  amp  amp   unserialize time  lt   json decode time    number format   json decode time    unserialize time - 1    100  2                   files   glob dirname   FILE        system cache        data   array     foreach   files as  file        if  is file  file              result   run test  file            if   result                 data      result                     uasort  data  function   a   b        return  a  Memory  KB     lt   b  Memory  KB           fields   array keys  data 0      gt    lt table gt       lt thead gt       lt tr gt           lt  php foreach   fields as  f      gt               lt td style  text-align  center  border 1px solid black padding  4px 8px font-weight bold font-size 1 1em  gt  lt     f    gt  lt  td gt           lt  php     gt       lt  tr gt       lt  thead gt        lt tbody gt       lt  php foreach   data as  d      gt           lt tr gt               lt  php foreach   d as  key   gt   value      gt                   lt  php  is win   strpos  key   Win      gt                   lt  php  color     is win  amp  amp   value     color  green font-weight bold           gt                   lt td style  text-align  center  vertical-align  middle  padding  3px 6px  border  1px solid gray   lt     color    gt   gt  lt     value      is win  amp  amp   value                 gt  lt  td gt               lt  php     gt           lt  tr gt       lt  php     gt       lt  tbody gt   lt  table gt

User · Answer

Seems like serialize is the one I m going to use for 2 reasons    Someone pointed out that unserialize is faster than json decode and a  read  case sounds more probable than a  write  case  I ve had trouble with json encode when having strings with invalid UTF-8 characters  When that happens the string ends up being empty causing loss of information

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If you are caching information that you will ultimately want to  include  at a later point in time  you may want to try using var export  That way you only take the hit in the  serialize  and not in the  unserialize

User · Answer

JSON is better if you want to backup Data and restore it on a different machine or via FTP   For example with serialize if you store data on a Windows server  download it via FTP and restore it on a Linux one it could not work any more due to the charachter re-encoding  because serialize stores the length of the strings and in the Unicode   UTF-8 transcoding some 1 byte charachter could became 2 bytes long making the algorithm crash

[php] Preferred method to store PHP arrays (json_encode vs serialize)

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