Can t use method return value in write context

Question

I would think the following piece of code should work  but it doesn t  Edited  Now works in PHP 5 5     if   empty  r- gt getError       Where getError   is simply   public function getError         return  this- gt error      Yet I end up with this error      can t use method return value in write context   What does this mean  Isn t this just a read

User · Answer

As pointed out by others  it s a  weird  limitation of empty      For most purproses  doing this is equal as calling empty  but this works   if   r- gt getError

User · Answer

I usually create a global function called is empty   just to get around this issue  function is empty  var      return empty  var       Then anywhere I would normally have used empty   I just use is empty

User · Answer

Prior to PHP 5 5  the the PHP docs used to say   empty   only checks variables as anything else will result in a parse error  In PHP  lt  5 5 you weren t able use empty   directly on a function s return value   Instead  you could assign the return from getError   to a variable and run empty   on the variable  In PHP  gt   5 5 this is no longer necessary

User · Answer

The alternative way to check if an array is empty could be   count  array  gt 0   It works for me without that error

User · Answer

Note  This is a very high voted answer with a high visibility  but please note that it promotes bad  unnecessary coding practices  See  Kornel s answer for the correct way  Note  2  I endorse the suggestions to use  Kornel s answer  When I wrote this answer three years ago  I merely meant to explain the nature of the error  not necessarily endorse the alternative   The code snippet below is not recommended    It s a limitation of empty   in PHP versions below 5 5   Note  empty   only checks variables as anything else will result in a parse error  In other words  the following will not work  empty trim  name     You d have to change to this    Not recommended  just illustrates the issue  err    r- gt getError    if   empty  err

User · Answer

empty   needs to access the value by reference  in order to check whether that reference points to something that exists   and PHP before 5 5 didn t support references to temporary values returned from functions   However  the real problem you have is that you use empty   at all  mistakenly believing that  empty  value is any different from  false    Empty is just an alias for  isset  thing       thing  When the thing you re checking always exists  in PHP results of function calls always exist   the empty   function is nothing but a negation operator   PHP doesn t have concept of emptyness  Values that evaluate to false are empty  values that evaluate to true are non-empty  It s the same thing  This code    x   something    if  empty  x         and this    x   something    if    x        has always the same result  in all cases  for all datatypes  because  x is defined empty   is redundant    Return value from the method always exists  even if you don t have return statement  return value exists and contains null   Therefore   if   empty  r- gt getError       is logically equivalent to   if   r- gt getError

User · Answer

I m not sure if this would be a common mistake  but if you do something like   var    value      value2    this will also produce the same error  Can t use method return value in write context  You can t have an   and a    in the same statement  You can use one or the other  but not both  Note  I understand this is unrelated to the actual code in the question  however this question is the top result when searching for the error message  so I wanted to post it here for completeness

User · Answer

The issue is this  you want to know if the error is not empty   public function getError         return  this- gt error      Adding a method isErrorSet   will solve the problem   public function isErrorSet         if  isset  this- gt error   amp  amp   empty  this- gt error             return true        else           return false            Now this will work fine with this code with no notice   if     x- gt isErrorSet           echo  x- gt getError

[php] Can't use method return value in write context

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