How can I generate a 6 digit unique number

Question

How can I generate a 6 digit unique number  I have verification mechanisms in place to check for duplicate entries

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If you want it to start at 000001 and go to 999999    num str   sprintf   06d   mt rand 1  999999      Mind you  it s stored as a string

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You can use  uniq   round microtime true    it generates 10 digit base on time which is never be duplicated

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six digit random number   mt rand 100000  999999     As all numbers between 100 000 and 999 999 are six digits  of course

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lt  php echo rand 100000 999999     gt   you can  generate random number

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Among the answers given here before this one  the one by  quot Yes Barry quot  is the most appropriate one  random int 100000  999999   Note that here we use random int  which was introduced in PHP 7 and uses a cryptographic random generator  something that is important if you want random codes to be hard to guess  random bytes was also introduced in PHP 7 and likewise uses a cryptographic random generator  Many other solutions for random value generation  including those involving time    microtime    uniqid    rand    mt rand    str shuffle    and array rand    are much more predictable and are unsuitable if the random string will serve as a password  a bearer credential  a nonce  a session identifier  a  quot verification code quot  or  quot confirmation code quot   or another secret value  The code above generates a string of 6 decimal digits  If you want to use a bigger character set  such as all upper-case letters  all lower-case letters  and the 10 digits   this is a more involved process  but you have to use random int or random bytes rather than rand    mt rand    str shuffle    etc   if the string will serve as a password  a  quot confirmation code quot   or another secret value  See an answer to a related question  and see also  generating a random code in php  I also list other things to keep in mind when generating unique identifiers  especially random ones

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lt  php  file    count txt      get the number from the file  uniq   file get contents  file      add  1  id    uniq   1       add that new value to text file again for next use file put contents  file   id       your unique id ready echo  id    gt    i hope this will work fine  i use the same technique in my website

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This will generate random 6 digit number  x000D   x000D   lt  php x000D      mt rand 100000 999999   x000D    gt  x000D   x000D   x000D

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I would use an algorithm  brute force could be as follows   First time through loop  Generate a random number between 100 000 through 999 999 and call that x1  Second time through the loop Generate a random number between 100 000 and x1 call this xt2  then generate a random number between x1 and 999 999 call this xt3  then randomly choose x2 or x3  call this x2  Nth time through the loop Generate random number between 100 000 and x1  x1 and x2  and x2 through 999 999 and so forth     watch out for endpoints  also watch out for x1

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Another one   str pad mt rand 0  999999   6   0   STR PAD LEFT     Anyway  for uniqueness  you will have to check that your number hasn t been already used   You tell that you check for duplicates  but be cautious since when most numbers will be used  the number of  attempts   and therefore the time taken  for getting a new number will increase  possibly resulting in very long delays  amp  wasting CPU resources   I would advise  if possible  to keep track of available IDs in an array  then randomly choose an ID among the available ones  by doing something like this  if ID list is kept in memory     arrayOfAvailableIDs   array map function  nb        return str pad  nb  6   0   STR PAD LEFT      range 0  999999      nbAvailableIDs   count  arrayOfAvailableIDs       pick a random ID   newID   array splice  arrayOfAvailableIDs  mt rand 0   nbAvailableIDs-1   1    nbAvailableIDs--    You can do something similar even if the ID list is stored in a database

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In PHP 7 0  I would suggest random int  min   max  over mt rand      randomSixDigitInt    random int 100000  999999     From php net      Caution   This function does not generate cryptographically secure values  and should not be used for cryptographic purposes  If you need a cryptographically secure value  consider using random int    random bytes    or openssl random pseudo bytes   instead    So this depends mostly on context   I ll also add that as of PHP 7 1 0 rand   is now an alias to mt rand     Cheers

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Try this using uniqid and hexdec  echo hexdec uniqid

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characters    123456789    charactersLength   strlen  characters    randomString       for   i   0   i  lt  6   i           randomString     characters rand 0   charactersLength - 1       pin  randomString

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Here s another one   substr number format time     rand   0        0 6

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There are some great answers  but many use functions that are flagged as not cryptographically secure  If you want a random 6 digit number that is cryptographically secure you can use something like this   key   random int 0  9999999    key   str pad  key  6  0  STR PAD LEFT   return  key   This will also include numbers like 000182 and others that would otherwise be excluded from the other examples

[php] How can I generate a 6 digit unique number?

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