PHP - Extracting a property from an array of objects

Question

I ve got an array of cats objects    cats   Array                0    gt  stdClass Object                                id    gt  15                         1    gt  stdClass Object                                id    gt  18                         2    gt  stdClass Object                                id    gt  23                   and I want to extract an array of cats  IDs in 1 line  not a function nor a loop     I was thinking about using array walk with create function but I don t know how to do it   Any idea

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You can do it easily with ouzo goodies   result   array map Functions  extract  - gt id   arr     or with Arrays  from ouzo goodies    result   Arrays  map  arr  Functions  extract  - gt id     Check out  http   ouzo readthedocs org en latest utils functions html extract  See also functional programming with ouzo  I cannot post a link

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If you have PHP 5 5 or later  the best way is to use the built in function array column      idCats   array column  cats   id      But the son has to be an array or converted to an array

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array that contain records and id is what we want to fetch a  ids   array column  array   id

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object   new stdClass         object- gt id   1        object2   new stdClass         object2- gt id   2        objects              object           object2              ids   array map function   object                 var YourEntity  object            return  object- gt id             Or even if you have public methods            return  object- gt getId           objects     Output   1  2

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The solution depends on the PHP version you are using  At least there are 2 solutions   First   Newer PHP versions   As  JosepAlsina said before the best and also shortest solution is to use array column as following    catIds   array column  objects   id      Notice  For iterating an array containing  stdClasses as used in the question it is only possible with PHP versions  gt   7 0  But when using an array containing arrays you can do the same since PHP  gt   5 5   Second  Older PHP versions    Greg said in older PHP versions it is possible to do following    catIds   array map create function   o    return  o- gt id      objects     But beware  In newer PHP versions  gt   5 3 0 it is better to use Closures  like followed    catIds   array map function  o    return  o- gt id      objects       The difference  First solution creates a new function and puts it into your RAM  The garbage collector does not delete the already created and already called function instance out of memory for some reason  And that regardless of the fact  that the created function instance can never be called again  because we have no pointer for it  And the next time when this code is called  the same function will be created again  This behavior slowly fills your memory     Both examples with memory output to compare them   BAD  while  true         objects   array map create function   o    return  o- gt id      objects        echo memory get usage       n        sleep 1         the output 4235616 4236600 4237560 4238520       GOOD  while  true         objects   array map function  o    return  o- gt id      objects        echo memory get usage       n        sleep 1         the output 4235136 4235168 4235168 4235168         This may also be discussed here  Memory leak   Is Garbage Collector doing right when using   39 create function  39  within   39 array map  39

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Warning create function   has been DEPRECATED as of PHP 7 2 0  Relying on this function is highly discouraged   You can use the array map   function  This should do it   catIds   array map create function   o    return  o- gt id      objects     As  Relequestual writes below  the function is now integrated directly in the array map  The new version of the solution looks like this   catIds   array map function  o    return  o- gt id     objects

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CODE   lt  php    setup test array   cats   array     cats      object  array  id    gt  15    cats      object  array  id    gt  18    cats      object  array  id    gt  23    function extract ids  array   array           ids   array        foreach   array as  object             ids      object- gt id            return  ids      cat ids   extract ids  cats   var dump  cats   var dump  cat ids      gt    OUTPUT    var dump  cats   array 3       0   gt    object stdClass  1  1          id    gt      int 15         1   gt    object stdClass  2  1          id    gt      int 18         2   gt    object stdClass  3  1          id    gt      int 23           var dump  cat ids   array 3       0   gt    int 15     1   gt    int 18     2   gt    int 23      I know its using a loop  but it s the simplest way to do it  And using a function it still ends up on a single line

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function extract ids  cats        res   array        foreach  cats as  k  gt  v             res     v- gt id            return  res     and use it in one line    ids   extract ids  cats

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The create function   function is deprecated as of php v7 2 0  You can use the array map   as given   function getObjectID  obj       return  obj- gt id      IDs   array map  getObjectID     array of object     Alternatively  you can use array column   function which returns the values from a single column of the input  identified by the column key  Optionally  an index key may be provided to index the values in the returned array by the values from the index key column of the input array  You can use the array column as given    IDs   array column  array of object    id

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Warning create function   has been DEPRECATED as of PHP 7 2 0  Relying on this function is highly discouraged    Builtin loops in PHP are faster then interpreted loops  so it actually makes sense to make this one a one-liner    result   array    array walk  cats  create function   value   key   amp  result     result      value- gt id      result

[php] PHP - Extracting a property from an array of objects

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