Invalid argument supplied for foreach

Question

It often happens to me to handle data that can be either an array or a null variable and to feed some foreach with these data    values   get values     foreach   values as  value             When you feed a foreach with data that are not an array  you get a warning      Warning  Invalid argument supplied for foreach   in         Assuming it s not possible to refactor the get values   function to always return an array  backward compatibility  not available source code  whatever other reason   I m wondering which is the cleanest and most efficient way to avoid these warnings    Casting  values to array Initializing  values to array Wrapping the foreach with an if Other  please suggest

User · Answer

There seems also to be a relation to the environment:

I had that "invalid argument supplied foreach()" error only in the dev environment, but not in prod (I am working on the server, not localhost).

Despite the error a var_dump indicated that the array was well there (in both cases app and dev).

The if (is_array($array)) around the foreach ($array as $subarray) solved the problem.

Sorry, that I cannot explain the cause, but as it took me a while to figure a solution I thought of better sharing this as an observation.

User · Answer

Exceptional case for this notice occurs if you set array to null inside foreach loop   if  is array  values         foreach   values as  value                 values   null   WARNING

User · Answer

I am not sure if this is the case but this problem seems to occur a number of times when migrating wordpress sites or migrating dynamic sites in general  If this is the case make sure the hosting you are migrating to uses the same PHP version your old site uses   If you are not migrating your site and this is just a problem that has come up try updating to PHP 5  This takes care of some of these problems  Might seem like a silly solution but did the trick for me

User · Answer

Try this     Force array  dataArr   is array  dataArr     dataArr   array  dataArr   foreach   dataArr as  val      echo  val

User · Answer

How about this solution    type   gettype  your iteratable    types   array       array        object      if  in array  type   types            foreach code comes here

User · Answer

First of all  every variable must be initialized  Always  Casting is not an option  if get values    can return different type variable  this value must be checked  of course

User · Answer

What about defining an empty array as fallback if get value   is empty  I can t think of a shortest way    values   get values           foreach   values as  value

User · Answer

Personally I find this to be the most clean - not sure if it s the most efficient  mind   if  is array  values     is object  values         foreach   values as  value                              The reason for my preference is it doesn t allocate an empty array when you ve got nothing to begin with anyway

User · Answer

More concise extension of  Kris s code  function secure iterable  var        return is iterable  var     var   array       foreach  secure iterable  values  as  value           do stuff        especially for using inside template code    lt  php foreach  secure iterable  values  as  value     gt           lt  php endforeach    gt

User · Answer

foreach   arr       as  elem           Do something    This doesen t check if it is an array  but skips the loop if the variable is null or an empty array

User · Answer

Please do not depend on casting as a solution  even though others are suggesting this as a valid option to prevent an error  it might cause another one   Be aware  If you expect a specific form of array to be returned  this might fail you  More checks are required for that      E g  casting a boolean to an array  array bool  will NOT result in an empty array  but an array with one element containing the boolean value as an int   0  gt 0  or  0  gt 1     I wrote a quick test to present this problem   Here is a backup Test in case the first test url fails    Included are tests for  null  false  true  a class  an array and undefined     Always test your input before using it in foreach  Suggestions     Quick type checking   array   is array  var  or is object  var     var        Type hinting arrays in methods before using a foreach and specifying return types Wrapping foreach within if Using try  catch     blocks Designing proper code   testing before production releases To test an array against proper form you could use array key exists on a specific key  or test the depth of an array  when it is one     Always extract your helper methods into the global namespace in a way to reduce duplicate code

User · Answer

i would do the same thing as Andy but i ld use the  empty  function   like so   if empty  yourArray    echo  lt p gt There s nothing in the array      lt  p gt     else   foreach   yourArray as  current array item            do something with the current array item here

User · Answer

I ll use a combination of empty  isset and is array as   array     dog    cat    lion     if   empty  array   amp  amp  isset  array   amp  amp  is array  array          loop     foreach   array as  values            echo  values

User · Answer

Use is array function  when you will pass array to foreach loop   if  is array  your variable       foreach   your variable as  item         your code

User · Answer

values   get values     foreach   array   values as  value             Problem is always null and Casting is in fact the cleaning solution

User · Answer

Warning invalid argument supplied for foreach   display tweets  go to  wp-content plugins display-tweets-php  Then insert this code on line number 591  It will run perfectly   if  is array  tweets         foreach   tweets as  tweet

User · Answer

How about this one  lot cleaner and all in single line   foreach   array   items as  item

User · Answer

If you re using php7 and you want to handle only undefined errors this is the cleanest IMHO   array    1 2 3 4   foreach    array       as  item       echo  item

User · Answer

I usually use a construct similar to this          Determine if a variable is iterable  i e  can be used to loop over         return bool     function is iterable  var        return  var     null           amp  amp   is array  var                   var instanceof Traversable                  var instanceof Iterator                  var instanceof IteratorAggregate                    values   get values     if  is iterable  values         foreach   values as  value                   do stuff              Note that this particular version is not tested  its typed directly into SO from memory   Edit  added Traversable check

[php] Invalid argument supplied for foreach()

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