PHP: is_null - Manual

User Contributed Notes
is_null

disappear at dissolution dot ath dot cx
08-May-2005 10:51


i wrote a small case study to compare is_null / == NULL / === NULL



Here's the code ::



<?php



    $Array = array ( 0 , '' , FALSE , NULL ) ;

    $ArrayCount = count ( $Array ) ;



    $String .= '$Array = ' . "array ( 0 , '' , FALSE , NULL ) <br><br>" ;



    for ( $i = 0 ; $i < $ArrayCount ; $i++ )



    {



        if ( $Array [ $i ] == NULL )



        {



            $String .= '$Array [ $i ] == NULL :: $Array [ ' . $i . ' ] <br>' ;



        }



        if ( $Array [ $i ] === NULL )



        {



            $String .= '$Array [ $i ] === NULL :: $Array [ ' . $i . ' ] <br>' ;



        }



        if ( is_null ( $Array [ $i ] ) )



        {



            $String .= 'is_null ( $Array [ $i ] ) :: $Array [ ' . $i . ' ] <br>' ;



        }



    }



    echo $String ;



?>



Here's the results i got ::



$Array = array ( 0 , '' , FALSE , NULL )



$Array [ $i ] == NULL :: $Array [ 0 ]

$Array [ $i ] == NULL :: $Array [ 1 ]

$Array [ $i ] == NULL :: $Array [ 2 ]

$Array [ $i ] == NULL :: $Array [ 3 ]

$Array [ $i ] === NULL :: $Array [ 3 ]

is_null ( $Array [ $i ] ) :: $Array [ 3 ]

jbeninger at nospam tiberDot ca
11-Apr-2004 04:18


Regarding the function that returns a default value if the passed value is null: I like my functions names to bear resemblance to their function (Nz doesn't really pass that test).  



I've got a similar function but have called it "if_null" - after the SQL function that serves the same purpose.

michael at cannonbose dot com
30-Dec-2003 11:42


Regarding avoidance of NULLs in your MySQL queries, why not use  IS NULL and IS NOT NULL in your WHERE clauses.



SELECT * 

FROM someDatabase 

WHERE someAttribute IS NOT NULL



Cheers,



Michael

galardi at dii dot unisi dot it
19-Aug-2002 12:43


The following function is useful for set a variable to a default value the case it contains null:



function Nz($TestVar,$ValueIfNull)

{

   if (is_null($TestVar))

      return $ValueIfNull;

    else

      return $TestVar;

}



I have used it to ensure to always write something in the cells of a table; otherwise Netscape doesn't show the color of cell background. Ex:



<TD valign="top" BGCOLOR="#F0F0F0">

<?echo Nz($row2["Name"],"&nbsp;");?>

</TD>

dstone[at]NOSPAMviatraining.com
07-Jun-2002 08:19


The above example is a little wrong. An empty value is not equivalent to null in mysql. To get not null in mysql use "... where column is not null"



If you are doing a left join in mysql, no matched entry returns a null, where if you had a matched entry and were asking about a text field, '' might match, so != '' is different than is not null

thepissboy at hotmail dot com
06-May-2002 11:00


After pulling out most of my hair weeding through really unintelligible crap: 



HERE'S AN EASY WAY TO ELIMINATE NULL VALUES FROM YOUR ARRAYS!!



$result = mysql_query("SELECT * FROM someDatabase WHERE page_title != ''",$db);

    if ($myrow = mysql_fetch_array($result)) {

    

    printf("%s\n", $myrow["page_title"]);

    }

    

    else {

    

    printf("Scratch head");

    }



It's all in the SQL Query line. The code says don't bring back anything that's empty!!!!



So hopefully, some of us will be able to get back to being in a hurry.

uioreanu at hotmail dot com
23-Mar-2001 08:36


Don't try to test


if ($intSomething==NULL) {


 ...


}


use is_null() instead.


The first statement misses 0 values.





Regards,


Calin





[Ed. note: this is because == tests for equivalence of value, but not type. NULL evaluates to 


false, as does 0, so NULL == 0 is true--even though 0 is type int and NULL is type null. 


You should use either is_null() as noted or ===, which returns true only if its operands are 


equal and of the same type.]

is_null

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Parameters

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