Possible Duplicate:
php == vs === operator
i have the following code fragment and it doesn't make sense to me why would NULL be evaluated in 3 different ways. Consider the variable $uploaded_filenames_array
as UNKNOWN - we don't know whether it's still an array or a NULL. That's what we are trying to check.
//-----------------------------------------------
if (is_null($uploaded_filenames_array)){
echo "is_null";
}
else{
echo "is_NOT_null";
}
//-----------------------------------------------
if ($uploaded_filenames_array == NULL){
echo "NULL stuff";
}
else{
echo "not NULL stuff";
}
//-----------------------------------------------
if ($uploaded_filenames_array === NULL){
echo "NULL identity";
}
else{
echo "not NULL identity";
}
//-----------------------------------------------
i am getting the following response:
is_NOT_null
NULL stuff
not NULL identity
can somebody help to understand what is the programmatic difference between these 3 ways of checking NULL?
It is an identical comparison operator and it returns true if the value of $x is equal to NULL. Null is a special data type in PHP which can have only one value that is NULL. A variable of data type NULL is a variable that has no value assigned to it.
NULL and empty - PHP TutorialNull is a fancy term for nothing, for not having a value. It's not zero, it's not an empty string, it's the actual lack of a value. I mean, if we can set a value into a variable, then we also have to have some way to talk about the fact that variable might not have a value at all.
NULL essentially means a variable has no value assigned to it; false is a valid Boolean value, 0 is a valid integer value, and PHP has some fairly ugly conversions between 0 , "0" , "" , and false . Show activity on this post. Null is nothing, False is a bit, and 0 is (probably) 32 bits.
is_null($a)
is same as $a === null
.
($a === null
is bit faster than is_null($a)
for saving one function call, but it doesn't matter, just choose the style you like.)
For the difference of ===
and ==
, read PHP type comparison tables
$a === null
be true only if $a
is null
.
But for ==
, the below also returns true
.
null == false
null == 0
null == array()
null == ""
You should read this http://php.net/manual/en/language.operators.comparison.php. Also no need to use is_null
function to check only on NULL
. ===
is faster...
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