PHP s array map including keys

Question

Is there a way of doing something like this    test array   array  first key    gt   first value                         second key    gt   second value     var dump array map function  a   b    return   a loves  b                array keys  test array             array values  test array       But instead of calling array keys and array values  directly passing the  test array variable   The desired output is   array 2       0   gt    string 27   first key loves first value     1   gt    string 29   second key loves second value

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I ll add yet another solution to the problem using version 5 6 or later  Don t know if it s more efficient than the already great solutions  probably not   but to me it s just simpler to read    myArray          key0    gt  0       key1    gt  1       key2    gt  2     array combine      array keys  myArray       array map          function   intVal                return strval  intVal                       myArray            Using strval   as an example function in the array map  this will generate   array 3        key0    gt    string 1   0      key1    gt    string 1   1      key2    gt    string 1   2      Hopefully I m not the only one who finds this pretty simple to grasp  array combine creates a key   gt  value array from an array of keys and an array of values  the rest is pretty self explanatory

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I see it s missing the obvious answer    function array map assoc        if func num args    lt  2  throw new  BadFuncionCallException  Missing parameters          args   func get args         callback    args 0        if  is callable  callback   throw new  InvalidArgumentException  First parameter musst be callable          arrays   array slice  args  1        array walk  arrays  function  amp  a            a    array  a          reset  a                 results   array         max length   max array map  count    arrays          arrays   array map function  pole  use   max length           return array pad  pole   max length  null           arrays        for  i 0   i  lt   max length   i              elements   array            foreach  arrays as  amp  v                elements     each  v                     unset  v             out   call user func array  callback   elements            if  out     null  continue            val   isset  out 1      out 1    null           if isset  out 0                  results  out 0      val           else               results      val                       return  results      Works exactly like array map  Almost   Actually  it s not pure map as you know it from other languages  Php is very weird  so it requires some very weird user functions  for we don t want to unbreak our precisely broken worse is better approach   Really  it s not actually map at all  Yet  it s still very useful    First obvious difference from array map  is that the callback takes outputs of each   from every input array instead of value alone  You can still iterate through more arrays at once  Second difference is the way the key is handled after it s returned from callback  the return value from callback function should be array  new key    new value    Keys can and will be changed  same keys can even cause previous value being overwritten  if same key was returned  This is not common map behavior  yet it allows you to rewrite keys  Third weird thing is  if you omit key in return value  either by array 1   gt   value   or array null   value     new key is going to be assigned  as if  array      value was used  That isn t map s common behavior either  yet it comes handy sometimes  I guess  Fourth weird thing is  if callback function doesn t return a value  or returns null  the whole set of current keys and values is omitted from the output  it s simply skipped  This feature is totally unmappy  yet it would make this function excellent stunt double for array filter assoc  if there was such function  If you omit second element  1   gt        the value part  in callback s return  null is used instead of real value  Any other elements except those with keys 0 and 1 in callback s return are ignored  And finally  if lambda returns any value except of null or array  it s treated as if both key and value were omitted  so     new key for element is assigned null is used as it s value      WARNING  Bear in mind  that this last feature is just a residue of previous features and it is probably completely useless  Relying on this feature is highly discouraged  as this feature is going to be randomly deprecated and changed unexpectedly in future releases    NOTE  Unlike in array map  all non-array parameters passed to array map assoc  with the exception of first callback parameter  are silently casted to arrays   EXAMPLES     TODO  examples  anyone

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Another way of doing this with out  preserving keys    test array          first key        gt   first value        second key       gt   second value       f   function  ar        return array map          function  key   val                return    key  -   val                       array keys  ar            ar             -- WITHOUT preserving keys  res    f  test array     -- WITH preserving keys  res   array combine      array keys  test array        f  test array

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You can use map method from this array library to achieve exactly what you want as easily as   Arr  map  test array  function  a   b    return   a loves  b         also it preserves keys and returns new array  not to mention few different modes to fit your needs

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By  manual loop  I meant write a custom function that uses foreach  This returns a new array like array map does because the function s scope causes  array to be a copy   not a reference   function map  array  callable  fn      foreach   array as  k   gt   amp  v   v   call user func  fn   k   v     return  array      Your technique using array map with array keys though actually seems simpler and is more powerful because you can use null as a callback to return the key-value pairs   function map  array  callable  fn   null      return array map  fn  array keys  array    array

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YaLinqo library  is well suited for this sort of task  It s a port of LINQ from  NET which fully supports values and keys in all callbacks and resembles SQL  For example    mapped array   from  test array      - gt select function   v   k    return   k loves  v          - gt toArray      or just    mapped iterator   from  test array - gt select    k loves  v       Here     k loves  v   is a shortcut for full closure syntax which this library supports  toArray   in the end is optional  The method chain returns an iterator  so if the result just needs to be iterated over using foreach  toArray call can be removed     developed by me

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array        category1    gt   first category      category2    gt   second category         new   array map function  key   value      return  quot   key    gt    value  quot      array keys  array    array

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Based on eis s answer  here s what I eventually did in order to avoid messing the original array    test array   array  first key    gt   first value                        second key    gt   second value      result array   array    array walk  test array              function  a   b  use   amp  result array                 result array       b loves  a                   result array   var dump  result array

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A closure would work if you only need it once  I d use a generator   test array          quot first key quot    gt   quot first value quot         quot second key quot    gt   quot second value quot        x result    function array  arr        foreach   arr as  key   gt   value            yield  quot  key loves  value quot             test array    var dump iterator to array  x result        array 2          0   gt       string 27   quot first key loves first value quot        1   gt       string 29   quot second key loves second value quot        For something reusable  function xmap callable  cb  array  arr        foreach   arr as  key   gt   value            yield  cb  key   value            var dump iterator to array      xmap function  a   b    return  quot  a loves  b quot       test array

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I made this function  based on eis s answer   function array map   callback   arr        if   is callable  callback           return  arr        result   array walk  arr  function  amp  value   key  use   callback             value   call user func  callback   key   value                if    result          return false       return  arr      Example    test array   array  first key    gt   first value                     second key    gt   second value     var dump array map  function  key   value       return  key     loves      value      arr      Output   array      first key    gt   first key loves first value     second key    gt   second key loves second value       Off course  you can use array values to return exactly what OP wants   array values array map  function  key   value       return  key     loves      value      test array

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This is probably the shortest and easiest to reason about    states   array  az    gt   Arizona    al    gt   Alabama     array map function   short   long        return array           short    gt   short           long     gt   long           array keys  states    states       produces  array       array  short    gt   az    long    gt   Arizona          array  short    gt   al    long    gt   Alabama

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I d do something like this    lt  php         array map kv        An array mapping function to map with both keys and values         param  callback callable      A callback function  key   value  for mapping values      param  array array      An array for mapping      function array map kv callable  callback  array  array      return array map      function   key  use   callback   array          return  callback  key   array  key        callback  key   value             array keys  array             use it var dump array map kv function   key   value      return    key  loves   value       array     first key    gt   first value      second key    gt   second value           gt    Results   array 2       0   gt    string 27   first key loves first value     1   gt    string 29   second key loves second value

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Look here  There is a trivial solution   function array map2 callable  f  array  a        return array map  f  array keys  a    a       As stated in the question  array map already has exactly the functionality required  The other answers here seriously overcomplicate things  array walk is not functional   Usage   Exactly as you would expect from your example    test array   array  first key    gt   first value                         second key    gt   second value     var dump array map2 function  a   b    return   a loves  b       test array

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I always like the javascript variant of array map  The most simple version of it would be           param  array     array     param  callable  callback     return array     function arrayMap array  array  callable  callback         newArray            foreach   array as  key   gt   value                  newArray     call user func  callback   value   key   array              return  newArray      So now you can just pass it a callback function how to construct the values    testArray          first key    gt   first value         second key    gt   second value      var dump      arrayMap  testArray  function  value   key            return  key     loves      value

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This is how I ve implemented this in my project   function array map associative callable  callback   array           map original array keys  and call  callable with  key and value of  key from original array         return array map function  key  use   callback   array           return  callback  key   array  key           array keys  array

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Not with array map  as it doesn t handle keys   array walk does    test array   array  first key    gt   first value                        second key    gt   second value    array walk  test array  function  amp  a   b     a     b loves  a       var dump  test array       array 2           first key    gt       string 27   first key loves first value         second key    gt       string 29   second key loves second value         It does change the array given as parameter however  so it s not exactly functional programming  as you have the question tagged like that   Also  as pointed out in the comment  this will only change the values of the array  so the keys won t be what you specified in the question   You could write a function that fixes the points above yourself if you wanted to  like this   function mymapper  arrayparam   valuecallback       resultarr   array      foreach   arrayparam as  key   gt   value         resultarr      valuecallback  key   value         return  resultarr      test array   array  first key    gt   first value                        second key    gt   second value     new array   mymapper  test array  function  a   b    return   a loves  b       var dump  new array       array 2          0   gt       string 27   first key loves first value        1   gt       string 29   second key loves second value

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With PHP5 3 or later    test array   array  first key    gt   first value                         second key    gt   second value     var dump      array map          function  key  use   test array    return   key loves   test array  key                array keys  test array

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Here s my very simple  PHP 5 5-compatible solution  function array map assoc callable  f  array  a        return array column array map  f  array keys  a    a   1  0      The callable you supply should itself return an array with two values  i e  return  key  value   The inner call to array map therefore produces an array of arrays  This then gets converted back to a single-dimension array by array column  Usage  ordinals          first    gt   1st        second    gt   2nd        third    gt   3rd        func   function   k   v        return   new      k   new      v       var dump array map assoc  func   ordinals     Output array 3        quot new first quot    gt    string 7   quot new 1st quot      quot new second quot    gt    string 7   quot new 2nd quot      quot new third quot    gt    string 7   quot new 3rd quot     Partial application In case you need to use the function many times with different arrays but the same mapping function  you can do something called partial function application  related to    currying      which allows you to only pass in the data array upon invocation  function array map assoc partial callable  f        return function  array  a  use   f            return array column array map  f  array keys  a    a   1  0                  my mapping   array map assoc partial  func   var dump  my mapping  ordinals     Which produces the same output  given  func and  ordinals are as earlier  NOTE  if your mapped function returns the same key for two different inputs  the value associated with the later key will win  Reverse the input array and output result of array map assoc to allow earlier keys to win   The returned keys in my example cannot collide as they incorporate the key of the source array  which in turn must be unique    Alternative Following is a variant of the above  which might prove more logical to some  but requires PHP 5 6  function array map assoc callable  f  array  a        return array merge    array map  f  array keys  a    a       In this variant  your supplied function  over which the data array is mapped  should instead return an associative array with one row  i e  return  key   gt  value   The result of mapping the callable is then simply unpacked and passed to array merge  As earlier  returning a duplicate key will result in later values winning   n b  Alex83690 has noted in a comment that using array replace here in the stead of array merge would preserve integer keys  array replace does not modify the input array  so is safe for functional code   If you are on PHP 5 3 to 5 5  the following is equivalent  It uses array reduce and the binary   array operator to convert the resulting two-dimensional array down to a one-dimensional array whilst preserving keys  function array map assoc callable  f  array  a        return array reduce array map  f  array keys  a    a   function  array  acc  array  a            return  acc    a                 Usage Both of these variants would be used thus   ordinals          first    gt   1st        second    gt   2nd        third    gt   3rd        func   function   k   v        return   new      k   gt   new      v       var dump array map assoc  func   ordinals     Note the   gt  instead of   in  func  The output is the same as before  and each can be partially applied in the same way as before     Summary The goal of the original question is to make the invocation of the call as simple as possible  at the expense of having a more complicated function that gets invoked  especially  to have the ability to pass the data array in as a single argument  without splitting the keys and values  Using the function supplied at the start of this answer   test array     quot first key quot    gt   quot first value quot                   quot second key quot    gt   quot second value quot      array map assoc   function  callable  f  array  a        return array column array map  f  array keys  a    a   1  0        f   function   key   value        return   key   key     loves      value       var dump array values  array map assoc  f   test array      Or  for this question only  we can make a simplification to array map assoc   function that drops output keys  since the question does not ask for them   test array     quot first key quot    gt   quot first value quot                   quot second key quot    gt   quot second value quot      array map assoc   function  callable  f  array  a        return array map  f  array keys  a    a        f   function   key   value        return  key     loves      value      var dump  array map assoc  f   test array     So the answer is NO  you can t avoid calling array keys  but you can abstract out the place where array keys gets called into a higher-order function  which might be good enough

[php] PHP's array_map including keys

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