add to array if it isn t there already

Question

How do I add elements to an array only if they aren t in there already  I have the following    a array       organize the array foreach  array as  k  gt  v       foreach  v as  key  gt  value           if  key   key             a    value                     print r  a        Output  Array    0    gt  1  1    gt  2  2    gt  3  3    gt  1  4    gt  2  5    gt  3  6    gt  4  7    gt  5  8    gt  6      Instead  I want  a to consist of the unique values   I know I can use array unique to get the desired results but I just want to know

User · Answer

if   in array  value   a      a    value

User · Answer

if   in array           array push

User · Answer

Try adding as key instead of value   Adding an entry  function addEntry  entry         this- gt entries  entry    true      Getting all entries  function getEntries         return array keys  this- gt enties

User · Answer

Since there are a ton of ways to accomplish the desired results and so many people provided  in array   as an answer  and the OP already mentions the use of array unique  I would like to provide a couple alternatives   Using array diff  php    4 0 1    5  you can filter out only the new array values that don t exist  Alternatively you can also compare the keys and values with array diff assoc  http   php net manual en function array-diff php   currentValues   array 1  2    newValues   array 1  3  1  4  2   var dump array diff  newValues   currentValues      Result   Array        1    gt  3      3    gt  4     http   ideone com SWO3D1  Another method is using array flip to assign the values as keys and compare them using isset  which will perform much faster than in array with large datasets  Again this filters out just the new values that do not already exist in the current values    currentValues    1  2    newValues    1  3  1  4  2    a   array     checkValues   array flip  currentValues   foreach   newValues as  v        if   isset  checkValues  v               a      v            Result   Array        0    gt  3      1    gt  4     http   ideone com cyRyzN  With either method you can then use array merge to append the unique new values to your current values    http   ideone com JCakmR  http   ideone com bwTz2u   Result   Array        0    gt  1      1    gt  2      2    gt  3      3    gt  4

User · Answer

If you don t care about the ordering of the keys  you could do the following    array   YOUR ARRAY  unique   array    foreach   array as  a         unique  a     a

User · Answer

With array flip   it could look like this    flipped   array flip  opts    flipped  newValue    1   opts   array keys  flipped     With array unique   - like this    opts      newValue   opts   array values array unique  opts      Notice that array values           you need it if you re exporting array to JavaScript in JSON form  array unique   alone would simply unset duplicate keys  without rebuilding the remaining elements   So  after converting to JSON this would produce object  instead of array    gt  gt  gt  json encode array unique   a   b   b   c       gt     0   a   1   b   3   c      gt  gt  gt  json encode array values array unique   a   b   b   c        gt     a   b   c

User · Answer

You d have to check each value against in array    a array       organize the array by cusip foreach  array as  k  gt  v       foreach  v as  key  gt  value           if  in array  value   a             a    value

User · Answer

Easy to write  but not the most effective one    array   array unique array merge  array   array to append      This one is probably faster    array   array merge  array  array diff  array to append   array

User · Answer

Try this code  I got it from here   input   Array 1 2 3 1 2 3 4 5 6    input   array map  unserialize   array unique array map  serialize    input

User · Answer

You should use the PHP function in array  see http   php net manual en function in-array php    if   in array  value   array          array      value       This is what the documentation says about in array      Returns TRUE if needle is found in the array  FALSE otherwise

User · Answer

you can try using  in array    function insert value  value   amp   arr        if   in array  value    arr               arr      value

User · Answer

Taking Gumbo s idea  making the code work    array   array  111111   222222   3333333   4444   5555     AAAAAA    BBBBBB    CCC    DDDDDDD    EEEEEEEE    FFFFFF    GGG    AAAAAA    BBBBBB    CCC    DDDDDDD    EEEEEEEE    FFFFFF    GGG    222222     666666    777777    HHHH     print r  array     keys  array    foreach   array as  k   gt   v       if  isset  v  value                keys  v     k           unique   array    foreach   keys as  key         unique      array  key     print   lt br gt  lt br gt    print r  unique     Gives this   Array        0    gt  111111      1    gt  222222      2    gt  3333333      3    gt  4444      4    gt  5555      5    gt  AAAAAA      6    gt  BBBBBB      7    gt  CCC      8    gt  DDDDDDD      9    gt  EEEEEEEE      10    gt  FFFFFF      11    gt  GGG      12    gt  AAAAAA      13    gt  BBBBBB      14    gt  CCC      15    gt  DDDDDDD      16    gt  EEEEEEEE      17    gt  FFFFFF      18    gt  GGG      19    gt  222222      20    gt  666666      21    gt  777777      22    gt  HHHH    Array        0    gt  111111      1    gt  222222      2    gt  3333333      3    gt  4444      4    gt  5555      5    gt  AAAAAA      6    gt  BBBBBB      7    gt  CCC      8    gt  DDDDDDD      9    gt  EEEEEEEE      10    gt  FFFFFF      11    gt  GGG      12    gt  666666      13    gt  777777      14    gt  HHHH

User · Answer

Since you seem to only have scalar values an PHP   s array is rather a hash map  you could use the value as key to avoid duplicates and associate the  k keys to them to be able to get the original values    keys   array    foreach   array as  k   gt   v       if  isset  v  key                keys  value     k            Then you just need to iterate it to get the original values    unique   array    foreach   keys as  key         unique      array  key   key        This is probably not the most obvious and most comprehensive approach but it is very efficient as it is in O n    Using in array instead like others suggested is probably more intuitive  But you would end up with an algorithm in O n2   in array is in O n   that is not applicable  Even pushing all values in the array and using array unique on it would be better than in array  array unique sorts the values in O n  log n  and then removes successive duplicates

User · Answer

If you re okay with using shorthands in your code  instead of writing explicit if blocks  like some coding standards recommend   you can further simplify Marius Schulz s answer with this one-liner   in array   value   array      array       value

[php] add to array if it isn't there already

Examples related to php