Best way to clear a PHP array s values

Question

Which is more efficient for clearing all values in an array  The first one would require me to use that function each time in the loop of the second example   foreach   array as  i   gt   value        unset  array  i        Or this  foreach  blah blah as  blah         foo   array          do something      foo   null

User · Answer

Sadly I can t answer the other questions  don t have enough reputation  but I need to point something out that was VERY important for me  and I think it will help other people too   Unsetting the variable is a nice way  unless you need the reference of the original array   To make clear what I mean  If you have a function wich uses the reference of the array  for example a sorting function like  function special sort my array  amp  array         temporary list   create assoziative special list out of array  array        sort my list  temporary list        unset  array       foreach  temporary list as  k   gt   v                 array  k     v            it is not working  Be careful here  unset deletes the reference  so the variable  array is created again and filled correctly  but the values are not accessable from outside the function   So if you have references  you need to use  array   array   instead of unset  even if it is less clean and understandable

User · Answer

i have used unset   to clear the array but i have come to realize that unset   will render the array null hence the need to re-declare the array  like for example   lt  php       arr   array        array push  arr    foo        unset  arr      this will set the array to null hence you need the line below or redeclaring it       arr    array            do what ever you want here   gt

User · Answer

If you just want to reset a variable to an empty array  you can simply reinitialize it    foo   array      Note that this will maintain any references to it    foo   array 1 2 3    bar    amp  foo          foo   array       clear array var dump  bar      array 0      -- bar was cleared too    If you want to break any references to it  unset it first    foo   array 1 2 3    bar    amp  foo         unset  foo      break references  foo   array       re-initialize to empty array var dump  bar      array 3    1  2  3   --  bar is unchanged

User · Answer

Use array splice to empty an array and retain the reference     array splice  myArray  0

User · Answer

For PHP  gt   5 4 use  var         Not sure if it s faster than  var   array     but at least looks cleaner

User · Answer

Maybe simple  economic way  less signs to use       array         We can read in php manual       As of PHP 5 4 you can also use the short array syntax  which replaces array   with

User · Answer

Isn t unset   good enough   unset  array

User · Answer

The question is not really answered by the posts  Keeping the keys and clearing the values is the focus of the question  foreach  resultMasterCleaned  header   as  ekey   gt   eval         resultMasterCleaned  key   eval     quot  quot                       As in the case of a two dimensional array holding CSV values and to blank out a particular row  Looping through seems the only way

User · Answer

I see this questions is realla old  but for that problem I wrote a recursive function to unset all values in an array  Recursive because its possible that values from the given array are also an array  So that works for me   function empty array  amp   complete array        foreach  complete array as  ckey   gt   cvalue                if   is array  cvalue                  complete array  ckey                  else               empty array   complete array  ckey                         return  complete array       So with that i get the array with all keys and sub-arrays  but empty values

User · Answer

Like Zack said in the comments below you are able to simply re-instantiate it using    foo   array        foo is still here   If you want something more powerful use unset since it also will clear  foo from the symbol table  if you need the array later on just instantiate it again   unset  foo       foo is gone  foo   array        foo is here again

User · Answer

This is powerful and tested  unset  gradearray    re-set the array

User · Answer

How about  array name   array

User · Answer

I d say the first  if the array is associative  If not  use a for loop   for   i   0   i  lt  count  array    i      unset  array  i        Although if possible  using   array   array      To reset the array to an empty array is preferable

User · Answer

The unset function is useful when the garbage collector is doing its rounds while not having a lunch break   however unset function simply destroys the variable reference to the data  the data still exists in memory and PHP sees the memory as in use despite no longer having a pointer to it   Solution  Assign null to your variables to clear the data  at least until the garbage collector gets a hold of it    var   null    and then unset it in similar way   unset  var

[php] Best way to clear a PHP array's values

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