isset and empty - what to use

Question

Could you help me to improve my coding style    In some tasks I need to check - is variable empty or contains something  To solve this task  I usually do the following    Check - is this variable set or not  If it s set - I check - it s empty or not    lt  php      var    23       if  isset  var  amp  amp  empty  var            echo  not empty        else          echo  is not set or empty           gt    And I have a question - should I use isset   before empty   - is it necessary  TIA

User · Answer

var    abcdef   if isset  var        if  strlen  var   gt  0                do something  string length greater than zero         else             do something else  string length 0 or less          This is a simple example  Hope it helps   edit  added isset in the event a variable isn t defined like above  it would cause an error  checking to see if its first set at the least will help remove some headache down the road

User · Answer

In your particular case  if   var    You need to use isset if you don t know whether the variable exists or not  Since you declared it on the very first line though  you know it exists  hence you don t need to  nay  should not use isset   The same goes for empty  only that empty also combines a check for the truthiness of the value  empty is equivalent to  isset  var       var and  empty is equivalent to isset  var   amp  amp   var  or isset  var   amp  amp   var    true   If you only want to test a variable that should exist for truthiness  if   var  is perfectly adequate and to the point

User · Answer

Empty returns true if the var is not set  But isset returns true even if the var is not empty

User · Answer

It depends what you are looking for  if you are just looking to see if it is empty just use empty as it checks whether it is set as well  if you want to know whether something is set or not use isset   Empty checks if the variable is set and if it is it checks it for null      0  etc  Isset just checks if is it set  it could be anything not null  With empty  the following things are considered empty        an empty string  0  0 as an integer  0 0  0 as a float   0   0 as a string  NULL FALSE array    an empty array  var  var   a variable declared  but without a value in a class    From http   php net manual en function empty php    As mentioned in the comments the lack of warning is also important with empty    PHP Manual says     empty   is the opposite of  boolean  var  except that no warning is   generated when the variable is not set    Regarding isset  PHP Manual says     isset   will return FALSE if testing a variable that has been set to NULL     Your code would be fine as    lt  php      var    23       if   empty  var            echo  not empty        else          echo  is not set or empty           gt      For example    var        if empty  var      true because    is considered empty        if isset  var     true because var is set          if empty  otherVar     true because  otherVar is null        if isset  otherVar     false because  otherVar is not set

User · Answer

You can just use empty   - as seen in the documentation  it will return false if the variable has no value    An example on that same page     lt  php  var   0      Evaluates to true because  var is empty if  empty  var         echo   var is either 0  empty  or not set at all         Evaluates as true because  var is set if  isset  var         echo   var is set even though it is empty       gt    You can use isset if you just want to know if it is not NULL  Otherwise it seems empty   is just fine to use alone

User · Answer

Here are the outputs of isset   and empty   for the 4 possibilities  undeclared  null  false and true    a null   b false   c true   var dump array isset  z1  isset  a  isset  b  isset  c   true      z1 previously undeclared var dump array empty  z2  empty  a  empty  b  empty  c   true      z2 previously undeclared    array 4     0   gt  bool false   1   gt  bool false   2   gt  bool true   3   gt  bool true       array 4     0   gt  bool true   1   gt  bool true   2   gt  bool true   3   gt  bool false       You ll notice that all the  isset  results are opposite of the  empty  results except for case  b false  All the values  except null which isn t a value but a non-value  that evaluate to false will return true when tested for by isset and false when tested by  empty    So use isset   when you re concerned about the existence of a variable   And use empty when you re testing for true or false  If the actual type of emptiness matters  use is null and    0     false

[php] isset() and empty() - what to use

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