How to remove duplicate values from a multi-dimensional array in PHP

Question

How can I remove duplicate values from a multi-dimensional array in PHP   Example array   Array        0    gt  Array                0    gt  abc          1    gt  def             1    gt  Array                0    gt  ghi          1    gt  jkl             2    gt  Array                0    gt  mno          1    gt  pql             3    gt  Array                0    gt  abc          1    gt  def             4    gt  Array                0    gt  ghi          1    gt  jkl             5    gt  Array                0    gt  mno          1    gt  pql

User · Answer

An alternative to serialize and unique     test           abc   def          ghi   jkl          mno   pql          abc   def          ghi   jkl          mno   pql         result   array reduce       test      function  carry  item           if  in array  item  carry                 array push  carry  item                     return  carry                    var dump  result        php unique php array 3         0    gt          array 2                 0    gt                  string 3   abc               1    gt                  string 3   def                 1    gt          array 2                 0    gt                  string 3   ghi               1    gt                  string 3   jkl                 2    gt          array 2                   0    gt                    string 3   mno                 1    gt                    string 3   pql

User · Answer

I ve given this problem a lot of thought and have determined that the optimal solution should follow two rules    For scalability  modify the array in place  no copying to a new array For performance  each comparison should be made only once   With that in mind and given all of PHP s quirks  below is the solution I came up with  Unlike some of the other answers  it has the ability to remove elements based on whatever key s  you want  The input array is expected to be numeric keys    count array   count  input   for   i   0   i  lt   count array   i          if  isset  input  i              for   j    i 1   j  lt   count array   j                  if  isset  input  j                        this is where you do your comparison for dupes                 if   input  i   checksum       input  j   checksum                          unset  input  j                                                        The only drawback is that the keys are not in order when the iteration completes  This isn t a problem if you re subsequently using only foreach loops  but if you need to use a for loop  you can put  input   array values  input   after the above to renumber the keys

User · Answer

Simple solution   array unique  array  SORT REGULAR

User · Answer

I had a similar problem but I found a 100  working solution for it    lt  php     function super unique  array  key                temp array              foreach   array as  amp  v               if   isset  temp array  v  key                 temp array  v  key     amp   v                   array   array values  temp array          return  array            arr      arr 0   id   0   arr 0   titel    ABC    arr 1   id   1   arr 1   titel    DEF    arr 2   id   2   arr 2   titel    ABC    arr 3   id   3   arr 3   titel    XYZ    echo   lt pre gt    print r  arr   echo  unique                      lt br  gt    print r super unique  arr  titel        gt

User · Answer

If  remove duplicates  means  remove duplicates  but let one there   a solution might be to apply the array unique      on the  identifier column  first and then to remove in the original array all the keys  that have been removed from the column array    array                    id    gt   123            foo    gt   aaa            bar    gt   bbb                        id    gt   123            foo    gt   ccc            bar    gt   ddd                        id    gt   567            foo    gt   eee            bar    gt   fff             ids   array column  array   id     ids   array unique  ids    array   array filter  array  function   key   value  use   ids        return in array  value  array keys  ids       ARRAY FILTER USE BOTH     The result is   Array        0    gt  Array                        id    gt  123              foo    gt  aaa              bar    gt  bbb                 2    gt  Array                        id    gt  567              foo    gt  eee              bar    gt  fff

User · Answer

Since 5 2 9 you can use array unique   if you use the SORT REGULAR flag like so   array unique  array  SORT REGULAR     This makes the function compare elements for equality as if  a     b were being used  which is perfect for your case   Output  Array        0    gt  Array                        0    gt  abc              1    gt  def                 1    gt  Array                        0    gt  ghi              1    gt  jkl                 2    gt  Array                        0    gt  mno              1    gt  pql                Keep in mind  though  that the documentation states      array unique   is not intended to work on multi dimensional arrays

User · Answer

A very easy and logical way to Unique a multi dimension array is as follows   If you have array like this   Array        Key1    gt  Array                        0    gt  Value1              1    gt  Value2              2    gt  Value1              3    gt  Value3              4    gt  Value1                Key2    gt  Array                        0    gt  Value1              1    gt  Value2              2    gt  Value1              3    gt  Value3              4    gt  Value4               use foreach to solve this   foreach  array as  k  gt  v        unique array unique  v        array  k   unique      it will give you following result   Array        Key1    gt  Array                        0    gt  Value1              1    gt  Value2              3    gt  Value3                Key2    gt  Array                        0    gt  Value1              1    gt  Value2              3    gt  Value3              4    gt  Value4               and if you want to rearrange the order of the keys   foreach  array as  k  gt  v        unique  array values array unique  v         array  k   unique      This operation will give you arranged key values like this   Array        Key1    gt  Array                        0    gt  Value1              1    gt  Value2              2    gt  Value3                Key2    gt  Array                        0    gt  Value1              1    gt  Value2              2    gt  Value3              3    gt  Value4               I hope this will clear everything

User · Answer

Simple solution   array unique  array  SORT REGULAR

User · Answer

Array        0    gt  Array                        id    gt  1              name    gt  john                 1    gt  Array                        id    gt  2              name    gt  smith                 2    gt  Array                        id    gt  3              name    gt  john                 3    gt  Array                        id    gt  4              name    gt  robert                temp   array unique array column  array   name      unique arr   array intersect key  array   temp     This will remove the duplicate names from array  unique by key

User · Answer

Lots of person asked me how to make Unique multidimensional array  I have taken reference from your comment and it helps me   First of All  Thanks to  jeromegamez  daveilers for your solution  But every time i gave the answer  they asked me how this  serialize  and  unserialize  works  That s why i want to share the reason of this with you so that it will help more people to understand the concept behind this    I am explaining why we use  serialize  and  unserialize  in steps    Step 1  Convert the multidimensional array to one-dimensional array  To convert the multidimensional array to a one-dimensional array  first generate byte stream representation of all the elements  including nested arrays  inside the array  serialize   function can generate byte stream representation of a value  To generate byte stream representation of all the elements  call serialize   function inside array map   function as a callback function  The result will be a one dimensional array no matter how many levels the multidimensional array has   Step 2  Make the values unique  To make this one dimensional array unique  use array unique   function   Step 3  Revert it to the multidimensional array  Though the array is now unique  the values looks like byte stream representation  To revert it back to the multidimensional array  use unserialize   function    input   array map  unserialize   array unique array map  serialize    input       Thanks again for all this

User · Answer

I had a similar problem but I found a 100  working solution for it    lt  php     function super unique  array  key                temp array              foreach   array as  amp  v               if   isset  temp array  v  key                 temp array  v  key     amp   v                   array   array values  temp array          return  array            arr      arr 0   id   0   arr 0   titel    ABC    arr 1   id   1   arr 1   titel    DEF    arr 2   id   2   arr 2   titel    ABC    arr 3   id   3   arr 3   titel    XYZ    echo   lt pre gt    print r  arr   echo  unique                      lt br  gt    print r super unique  arr  titel        gt

User · Answer

Another way  Will preserve keys as well   function array unique multidimensional  input         serialized   array map  serialize    input        unique   array unique  serialized       return array intersect key  input   unique

User · Answer

An easy to read solution  probably not the most efficient   function arrayUnique  myArray       if  is array  myArray           return  myArray       foreach   myArray as  amp  myvalue            myvalue serialize  myvalue               myArray array unique  myArray        foreach   myArray as  amp  myvalue            myvalue unserialize  myvalue              return  myArray

User · Answer

The user comments on the array unique   documentation have many solutions to this  Here is one of them      kenrbnsn at rbnsn dot com   27-Sep-2005 12 09      Yet another Array Unique for multi-demensioned arrays  I ve only tested this on two-demensioned arrays  but it could probably be generalized for more  or made to use recursion       This function uses the serialize  array unique  and unserialize functions to do the work    function multi unique  array        foreach   array as  k   na           new  k    serialize  na        uniq   array unique  new       foreach  uniq as  k   ser           new1  k    unserialize  ser       return   new1       This is from http   ca3 php net manual en function array-unique php 57202

User · Answer

If you have an array like this  data   array    0    gt  array        subject    gt  a      object    gt  c     1    gt  array        subject    gt  b      object    gt  d     2    gt  array        subject    gt  d      object    gt  b     3    gt  array        subject    gt  d      object    gt  c     4    gt  array        subject    gt  c      object    gt  a     5    gt  array        subject    gt  c      object    gt  d       and you want to get arrays like this   data   array    0    gt  array        subject    gt  a      object    gt  c     1    gt  array        subject    gt  b      object    gt  d     2    gt  array        subject    gt  d      object    gt  c       or  data   array    0    gt  array        subject    gt  d      object    gt  b     1    gt  array        subject    gt  c      object    gt  a     2    gt  array        subject    gt  c      object    gt  d       a following code can help       data1   array         data1    data      for  q 0  q lt count  data   q                      for  p 0  p lt count  data1   p                                      if    data  q   subject       data1  p   object     amp  amp    data  q   object       data1  p   subject                                                        data1  p   subject      data  q   subject                                 data1  p   object      data  q   object                                                   data1   array values array map  unserialize   array unique array map  serialize    data1           data    data1

User · Answer

Lots of person asked me how to make Unique multidimensional array  I have taken reference from your comment and it helps me   First of All  Thanks to  jeromegamez  daveilers for your solution  But every time i gave the answer  they asked me how this  serialize  and  unserialize  works  That s why i want to share the reason of this with you so that it will help more people to understand the concept behind this    I am explaining why we use  serialize  and  unserialize  in steps    Step 1  Convert the multidimensional array to one-dimensional array  To convert the multidimensional array to a one-dimensional array  first generate byte stream representation of all the elements  including nested arrays  inside the array  serialize   function can generate byte stream representation of a value  To generate byte stream representation of all the elements  call serialize   function inside array map   function as a callback function  The result will be a one dimensional array no matter how many levels the multidimensional array has   Step 2  Make the values unique  To make this one dimensional array unique  use array unique   function   Step 3  Revert it to the multidimensional array  Though the array is now unique  the values looks like byte stream representation  To revert it back to the multidimensional array  use unserialize   function    input   array map  unserialize   array unique array map  serialize    input       Thanks again for all this

User · Answer

Here is another way  No intermediate variables are saved    We used this to de-duplicate results from a variety of overlapping queries    input   array map  unserialize   array unique array map  serialize    input

User · Answer

Based on the Answer marked as correct  adding my answer  Small code added just to reset the indices-   input   array values array map  unserialize   array unique array map  serialize    inputArray

User · Answer

As people are saying array unique   is very slow  here is a snippet I use for one level multidimensional array    serialized array   array map  serialize    input    foreach   serialized array as  key   gt   val          result  val    true      output   array map  unserialize    array keys  result       Reference first user contributed note of array unique   function page in php net

User · Answer

if you have an array like this    users is the name of the array   Array  gt    0    gt   array      user    gt   john      age    gt   23    1    gt   array     user    gt   jane     age    gt   20    2   gt   array     user    gt   john     age    gt   23    and you want to delete duplicates   then    serialized   array    for   i 0   i  lt  sizeof  users    i          test   in array  users  user     serialized       if   test    false           serialized      users  user               can be a solution  P

User · Answer

If you have an array like this  data   array    0    gt  array        subject    gt  a      object    gt  c     1    gt  array        subject    gt  b      object    gt  d     2    gt  array        subject    gt  d      object    gt  b     3    gt  array        subject    gt  d      object    gt  c     4    gt  array        subject    gt  c      object    gt  a     5    gt  array        subject    gt  c      object    gt  d       and you want to get arrays like this   data   array    0    gt  array        subject    gt  a      object    gt  c     1    gt  array        subject    gt  b      object    gt  d     2    gt  array        subject    gt  d      object    gt  c       or  data   array    0    gt  array        subject    gt  d      object    gt  b     1    gt  array        subject    gt  c      object    gt  a     2    gt  array        subject    gt  c      object    gt  d       a following code can help       data1   array         data1    data      for  q 0  q lt count  data   q                      for  p 0  p lt count  data1   p                                      if    data  q   subject       data1  p   object     amp  amp    data  q   object       data1  p   subject                                                        data1  p   subject      data  q   subject                                 data1  p   object      data  q   object                                                   data1   array values array map  unserialize   array unique array map  serialize    data1           data    data1

User · Answer

Array        0    gt  Array                        id    gt  1              name    gt  john                 1    gt  Array                        id    gt  2              name    gt  smith                 2    gt  Array                        id    gt  3              name    gt  john                 3    gt  Array                        id    gt  4              name    gt  robert                temp   array unique array column  array   name      unique arr   array intersect key  array   temp     This will remove the duplicate names from array  unique by key

User · Answer

if you have an array like this    users is the name of the array   Array  gt    0    gt   array      user    gt   john      age    gt   23    1    gt   array     user    gt   jane     age    gt   20    2   gt   array     user    gt   john     age    gt   23    and you want to delete duplicates   then    serialized   array    for   i 0   i  lt  sizeof  users    i          test   in array  users  user     serialized       if   test    false           serialized      users  user               can be a solution  P

User · Answer

Another way  Will preserve keys as well   function array unique multidimensional  input         serialized   array map  serialize    input        unique   array unique  serialized       return array intersect key  input   unique

User · Answer

Just use SORT REGULAR option as second parameter    uniqueArray   array unique  array  SORT REGULAR

User · Answer

I have tried this to remove the duplicates   array   array map  quot unserialize quot   array unique array map  quot serialize quot    array

User · Answer

Since 5 2 9 you can use array unique   if you use the SORT REGULAR flag like so   array unique  array  SORT REGULAR     This makes the function compare elements for equality as if  a     b were being used  which is perfect for your case   Output  Array        0    gt  Array                        0    gt  abc              1    gt  def                 1    gt  Array                        0    gt  ghi              1    gt  jkl                 2    gt  Array                        0    gt  mno              1    gt  pql                Keep in mind  though  that the documentation states      array unique   is not intended to work on multi dimensional arrays

User · Answer

As people are saying array unique   is very slow  here is a snippet I use for one level multidimensional array    serialized array   array map  serialize    input    foreach   serialized array as  key   gt   val          result  val    true      output   array map  unserialize    array keys  result       Reference first user contributed note of array unique   function page in php net

User · Answer

if you need to eliminate duplicates on specific keys  such as a mysqli id  here s a simple funciton  function search array compact  data  key        compact           foreach  data as  row           if  in array  row  key   compact                 compact      row                      return  compact      Bonus Points You can pass an array of keys and add an outer foreach  but it will be 2x slower per additional key

User · Answer

The user comments on the array unique   documentation have many solutions to this  Here is one of them      kenrbnsn at rbnsn dot com   27-Sep-2005 12 09      Yet another Array Unique for multi-demensioned arrays  I ve only tested this on two-demensioned arrays  but it could probably be generalized for more  or made to use recursion       This function uses the serialize  array unique  and unserialize functions to do the work    function multi unique  array        foreach   array as  k   na           new  k    serialize  na        uniq   array unique  new       foreach  uniq as  k   ser           new1  k    unserialize  ser       return   new1       This is from http   ca3 php net manual en function array-unique php 57202

User · Answer

The user comments on the array unique   documentation have many solutions to this  Here is one of them      kenrbnsn at rbnsn dot com   27-Sep-2005 12 09      Yet another Array Unique for multi-demensioned arrays  I ve only tested this on two-demensioned arrays  but it could probably be generalized for more  or made to use recursion       This function uses the serialize  array unique  and unserialize functions to do the work    function multi unique  array        foreach   array as  k   na           new  k    serialize  na        uniq   array unique  new       foreach  uniq as  k   ser           new1  k    unserialize  ser       return   new1       This is from http   ca3 php net manual en function array-unique php 57202

User · Answer

Just use SORT REGULAR option as second parameter    uniqueArray   array unique  array  SORT REGULAR

User · Answer

Based on the Answer marked as correct  adding my answer  Small code added just to reset the indices-   input   array values array map  unserialize   array unique array map  serialize    inputArray

User · Answer

I ve given this problem a lot of thought and have determined that the optimal solution should follow two rules    For scalability  modify the array in place  no copying to a new array For performance  each comparison should be made only once   With that in mind and given all of PHP s quirks  below is the solution I came up with  Unlike some of the other answers  it has the ability to remove elements based on whatever key s  you want  The input array is expected to be numeric keys    count array   count  input   for   i   0   i  lt   count array   i          if  isset  input  i              for   j    i 1   j  lt   count array   j                  if  isset  input  j                        this is where you do your comparison for dupes                 if   input  i   checksum       input  j   checksum                          unset  input  j                                                        The only drawback is that the keys are not in order when the iteration completes  This isn t a problem if you re subsequently using only foreach loops  but if you need to use a for loop  you can put  input   array values  input   after the above to renumber the keys

User · Answer

An alternative to serialize and unique     test           abc   def          ghi   jkl          mno   pql          abc   def          ghi   jkl          mno   pql         result   array reduce       test      function  carry  item           if  in array  item  carry                 array push  carry  item                     return  carry                    var dump  result        php unique php array 3         0    gt          array 2                 0    gt                  string 3   abc               1    gt                  string 3   def                 1    gt          array 2                 0    gt                  string 3   ghi               1    gt                  string 3   jkl                 2    gt          array 2                   0    gt                    string 3   mno                 1    gt                    string 3   pql

User · Answer

Another way  Will preserve keys as well   function array unique multidimensional  input         serialized   array map  serialize    input        unique   array unique  serialized       return array intersect key  input   unique

User · Answer

A very easy and logical way to Unique a multi dimension array is as follows   If you have array like this   Array        Key1    gt  Array                        0    gt  Value1              1    gt  Value2              2    gt  Value1              3    gt  Value3              4    gt  Value1                Key2    gt  Array                        0    gt  Value1              1    gt  Value2              2    gt  Value1              3    gt  Value3              4    gt  Value4               use foreach to solve this   foreach  array as  k  gt  v        unique array unique  v        array  k   unique      it will give you following result   Array        Key1    gt  Array                        0    gt  Value1              1    gt  Value2              3    gt  Value3                Key2    gt  Array                        0    gt  Value1              1    gt  Value2              3    gt  Value3              4    gt  Value4               and if you want to rearrange the order of the keys   foreach  array as  k  gt  v        unique  array values array unique  v         array  k   unique      This operation will give you arranged key values like this   Array        Key1    gt  Array                        0    gt  Value1              1    gt  Value2              2    gt  Value3                Key2    gt  Array                        0    gt  Value1              1    gt  Value2              2    gt  Value3              3    gt  Value4               I hope this will clear everything

User · Answer

If  remove duplicates  means  remove duplicates  but let one there   a solution might be to apply the array unique      on the  identifier column  first and then to remove in the original array all the keys  that have been removed from the column array    array                    id    gt   123            foo    gt   aaa            bar    gt   bbb                        id    gt   123            foo    gt   ccc            bar    gt   ddd                        id    gt   567            foo    gt   eee            bar    gt   fff             ids   array column  array   id     ids   array unique  ids    array   array filter  array  function   key   value  use   ids        return in array  value  array keys  ids       ARRAY FILTER USE BOTH     The result is   Array        0    gt  Array                        id    gt  123              foo    gt  aaa              bar    gt  bbb                 2    gt  Array                        id    gt  567              foo    gt  eee              bar    gt  fff

User · Answer

An easy to read solution  probably not the most efficient   function arrayUnique  myArray       if  is array  myArray           return  myArray       foreach   myArray as  amp  myvalue            myvalue serialize  myvalue               myArray array unique  myArray        foreach   myArray as  amp  myvalue            myvalue unserialize  myvalue              return  myArray

User · Answer

if you need to eliminate duplicates on specific keys  such as a mysqli id  here s a simple funciton  function search array compact  data  key        compact           foreach  data as  row           if  in array  row  key   compact                 compact      row                      return  compact      Bonus Points You can pass an array of keys and add an outer foreach  but it will be 2x slower per additional key

User · Answer

The user comments on the array unique   documentation have many solutions to this  Here is one of them      kenrbnsn at rbnsn dot com   27-Sep-2005 12 09      Yet another Array Unique for multi-demensioned arrays  I ve only tested this on two-demensioned arrays  but it could probably be generalized for more  or made to use recursion       This function uses the serialize  array unique  and unserialize functions to do the work    function multi unique  array        foreach   array as  k   na           new  k    serialize  na        uniq   array unique  new       foreach  uniq as  k   ser           new1  k    unserialize  ser       return   new1       This is from http   ca3 php net manual en function array-unique php 57202

User · Answer

Another way  Will preserve keys as well   function array unique multidimensional  input         serialized   array map  serialize    input        unique   array unique  serialized       return array intersect key  input   unique

User · Answer

I have tried this to remove the duplicates   array   array map  quot unserialize quot   array unique array map  quot serialize quot    array

User · Answer

Here is another way  No intermediate variables are saved    We used this to de-duplicate results from a variety of overlapping queries    input   array map  unserialize   array unique array map  serialize    input

[php] How to remove duplicate values from a multi-dimensional array in PHP

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