PHP function to generate v4 UUID

Question

So I ve been doing some digging around and I ve been trying to piece together a function that generates a valid v4 UUID in PHP  This is the closest I ve been able to come  My knowledge in hex  decimal  binary  PHP s bitwise operators and the like is nearly non existant  This function generates a valid v4 UUID up until one area  A v4 UUID should be in the form of      xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx   where y  is 8  9  A  or B  This is where the functions fails as it doesn t adhere to that   I was hoping someone with more knowledge than me in this area could lend me a hand and help me fix this function so it does adhere to that rule   The function is as follows    lt  php  function gen uuid       uuid   array     time low     gt  0     time mid     gt  0     time hi     gt  0     clock seq hi    gt  0     clock seq low    gt  0     node      gt  array          uuid  time low     mt rand 0  0xffff     mt rand 0  0xffff   lt  lt  16     uuid  time mid     mt rand 0  0xffff     uuid  time hi      4  lt  lt  12     mt rand 0  0x1000      uuid  clock seq hi      1  lt  lt  7     mt rand 0  128      uuid  clock seq low     mt rand 0  255     for   i   0   i  lt  6   i         uuid  node    i    mt rand 0  255         uuid   sprintf   08x- 04x- 04x- 02x 02x- 02x 02x 02x 02x 02x 02x      uuid  time low       uuid  time mid       uuid  time hi       uuid  clock seq hi       uuid  clock seq low       uuid  node   0      uuid  node   1      uuid  node   2      uuid  node   3      uuid  node   4      uuid  node   5        return  uuid       gt    Thanks to anyone that can help me out

User · Answer

My answer is based on comment uniqid user comment but it uses openssl random pseudo bytes function to generate random string instead of reading from  dev urandom  function guid          randomString   openssl random pseudo bytes 16        time low   bin2hex substr  randomString  0  4         time mid   bin2hex substr  randomString  4  2         time hi and version   bin2hex substr  randomString  6  2         clock seq hi and reserved   bin2hex substr  randomString  8  2         node   bin2hex substr  randomString  10  6                    Set the four most significant bits  bits 12 through 15  of the        time hi and version field to the 4-bit version number from        Section 4 1 3          see http   tools ietf org html rfc4122 section-4 1 3             time hi and version   hexdec  time hi and version        time hi and version    time hi and version  gt  gt  4       time hi and version    time hi and version   0x4000                  Set the two most significant bits  bits 6 and 7  of the        clock seq hi and reserved to zero and one  respectively               clock seq hi and reserved   hexdec  clock seq hi and reserved        clock seq hi and reserved    clock seq hi and reserved  gt  gt  2       clock seq hi and reserved    clock seq hi and reserved   0x8000       return sprintf   08s- 04s- 04x- 04x- 012s    time low   time mid   time hi and version   clock seq hi and reserved   node        guid

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on unix systems  use the system kernel to generate a uuid for you   file get contents   proc sys kernel random uuid     Credit Samveen on https   serverfault com a 529319 210994     Note   Using this method to get a uuid does in fact exhaust the entropy pool  very quickly  I would avoid using this where it would be called frequently

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In my search for a creating a v4 uuid  I came first to this page  then found this on http   php net manual en function com-create-guid php  function guidv4         if  function exists  com create guid       true          return trim com create guid                 data   openssl random pseudo bytes 16        data 6    chr ord  data 6    amp  0x0f   0x40      set version to 0100      data 8    chr ord  data 8    amp  0x3f   0x80      set bits 6-7 to 10     return vsprintf   s s- s- s- s- s s s   str split bin2hex  data   4        credit  pavel volyntsev  Edit  to clarify  this function will always give you a v4 uuid  PHP    5 3 0    When the com create guid function is available  usually only on Windows   it will use that and strip the curly braces   If not present  Linux   it will fall back on this strong random openssl random pseudo bytes function  it will then uses vsprintf to format it into v4 uuid

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Inspired by broofa s answer here   preg replace callback    xy     function   matches      return dechex  x      matches 0    mt rand 0  15     mt rand 0  15   amp  0x3   0x8         xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx      Or if unable to use anonymous functions   preg replace callback    xy     create function      matches      return dechex  x      matches 0    mt rand 0  15     mt rand 0  15   amp  0x3   0x8          xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx

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Use Symfony Polyfill   Uuid Then you can just generate uuid as native php function      uuid   uuid create UUID TYPE RANDOM     More about it  read in official Symfony blop post - https   symfony com blog introducing-the-new-symfony-uuid-polyfill

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From tom  on http   www php net manual en function uniqid php   r   unpack  v    fread fopen   dev random    r   16     uuid   sprintf   04x 04x- 04x- 04x- 04x- 04x 04x 04x        r 1    r 2    r 3    r 4   amp  0x0fff   0x4000       r 5   amp  0x3fff   0x8000   r 6    r 7    r 8

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Having searched for the exact same thing and almost implementing a version of this myself  I thought it was worth mentioning that  if you re doing this within a WordPress framework  WP has its own super-handy function for exactly this    myUUID   wp generate uuid4     You can read the description and the source here

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Instead of breaking it down into individual fields  it s easier to generate a random block of data and change the individual byte positions  You should also use a better random number generator than mt rand     According to RFC 4122 - Section 4 4  you need to change these fields    time hi and version  bits 4-7 of 7th octet   clock seq hi and reserved  bit 6  amp  7 of 9th octet    All of the other 122 bits should be sufficiently random    The following approach generates 128 bits of random data using openssl random pseudo bytes    makes the permutations on the octets and then uses bin2hex   and vsprintf   to do the final formatting   function guidv4  data        assert strlen  data     16         data 6    chr ord  data 6    amp  0x0f   0x40      set version to 0100      data 8    chr ord  data 8    amp  0x3f   0x80      set bits 6-7 to 10      return vsprintf   s s- s- s- s- s s s   str split bin2hex  data   4       echo guidv4 openssl random pseudo bytes 16      With PHP 7  generating random byte sequences is even simpler using random bytes     function guidv4  data   null         data    data    random bytes 16

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Anyone using composer dependencies  you might want to consider this library  https   github com ramsey uuid  It doesn t get any easier than this   Uuid  uuid4

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If you use CakePHP you can use their method CakeText  uuid    from the CakeText class to generate a RFC4122 uuid

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A slight variation on Jack s answer to add support for PHP  lt  7      Get an RFC-4122 compliant globaly unique identifier function get guid          data   PHP MAJOR VERSION  lt  7   openssl random pseudo bytes 16    random bytes 16        data 6    chr ord  data 6    amp  0x0f   0x40         Set version to 0100      data 8    chr ord  data 8    amp  0x3f   0x80         Set bits 6-7 to 10     return vsprintf   s s- s- s- s- s s s   str split bin2hex  data   4

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uuid   vsprintf   s s- s- s- s- s s s   str split bin2hex random bytes 16    4

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How about using mysql to generate the uuid for you    conn   new mysqli  servername   username   password   dbname   port     query    SELECT UUID     echo  conn- gt query  query - gt fetch row   0

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I m sure there s a more elegant way to do the conversion from binary to decimal for the 4xxx and yxxx portions   But if you want to use openssl random pseudo bytes as your crytographically secure number generator  this is what I use   return sprintf   s- s- 04x- 04x- s       bin2hex openssl random pseudo bytes 4        bin2hex openssl random pseudo bytes 2        hexdec bin2hex openssl random pseudo bytes 2     amp  0x0fff   0x4000      hexdec bin2hex openssl random pseudo bytes 2     amp  0x3fff   0x8000      bin2hex openssl random pseudo bytes 6

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Taken from this comment on the PHP manual  you could use this   function gen uuid         return sprintf    04x 04x- 04x- 04x- 04x- 04x 04x 04x              32 bits for  time low          mt rand  0  0xffff    mt rand  0  0xffff                16 bits for  time mid          mt rand  0  0xffff                16 bits for  time hi and version              four most significant bits holds version number 4         mt rand  0  0x0fff     0x4000              16 bits  8 bits for  clk seq hi res              8 bits for  clk seq low              two most significant bits holds zero and one for variant DCE1 1         mt rand  0  0x3fff     0x8000              48 bits for  node          mt rand  0  0xffff    mt rand  0  0xffff    mt rand  0  0xffff

[php] PHP function to generate v4 UUID

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