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php is null when empty? [duplicate]

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Does empty check for NULL PHP?

The empty() function returns true if the value of a variable evaluates to false . This could mean the empty string, NULL , the integer 0 , or an array with no elements. On the other hand, is_null() will return true only if the variable has the value NULL .

IS NULL condition in PHP?

The is_null() function checks whether a variable is NULL or not. This function returns true (1) if the variable is NULL, otherwise it returns false/nothing.

Is NULL true or false PHP?

NULL essentially means a variable has no value assigned to it; false is a valid Boolean value, 0 is a valid integer value, and PHP has some fairly ugly conversions between 0 , "0" , "" , and false . Show activity on this post. Null is nothing, False is a bit, and 0 is (probably) 32 bits.

IS NOT NULL PHP condition?

The isset() function is an inbuilt function in PHP which checks whether a variable is set and is not NULL. This function also checks if a declared variable, array or array key has null value, if it does, isset() returns false, it returns true in all other possible cases.


What you're looking for is:

if($variable === NULL) {...}

Note the ===.
When use ==, as you did, PHP treats NULL, false, 0, the empty string, and empty arrays as equal.


As is shown in the following table, empty($foo) is equivalent to $foo==null and is_null($foo) has the same function of $foo===null. The table also shows some tricky values regarding the null comparison. (ϕ denotes an uninitialized variables. )

         empty    is_null 
         ==null  ===null  isset   array_key_exists
      ϕ |   T   |   T   |   F   |   F   
   null |   T   |   T   |   F   |   T   
     "" |   T   |   F   |   T   |   T   
     [] |   T   |   F   |   T   |   T
      0 |   T   |   F   |   T   |   T      
  false |   T   |   F   |   T   |   T   
   true |   F   |   F   |   T   |   T   
      1 |   F   |   F   |   T   |   T   
     \0 |   F   |   F   |   T   |   T   

check == vs ===

'' == NULL would return true
0 == NULL would return true
false == null would return true

where as

'' === NULL would return false
0 === NULL would return false
false === NULL would return false


No it's not a bug. Have a look at the Loose comparisons with == table (second table), which shows the result of comparing each value in the first column with the values in the other columns:

    TRUE    FALSE   1       0       -1      "1"     "0"     "-1"    NULL    array() "php"   ""

    [...]    

""  FALSE   TRUE    FALSE   TRUE    FALSE   FALSE   FALSE   FALSE   TRUE    FALSE   FALSE   TRUE

There you can see that an empty string "" compared with false, 0, NULL or "" will yield true.

You might want to use is_null [docs] instead, or strict comparison (third table).


This is not a bug but PHP normal behavior. It happens because the == operator in PHP doesn't check for type.

'' == null == 0 == false

If you want also to check if the values have the same type, use === instead. To study in deep this difference, please read the official documentation.