Switch statement

[snorky]

I'm not getting the results I expect. It must be the way I'm defining the cases:

switch ($emdiff)
{
case "":					// emdiff is blank 
	( ... do some stuff ... )
	break;

case "!=''" and "NOT NULL":	        // emdiff is NOT blank and IS NOT NULL
	( ... do some different stuff ... )
	break;

case "NULL": 				// emdiff IS NULL 
	( ... do nothing ... )
	break;									
}

In a switch statement, how do I deal with

• an empty field
  
• a non-empty field whose value is NULL
  
• a non-empty field whose value is NOT NULL
  

[Andy-H]

Only run the statement if the variable is set.

 

if ( isSet($var) )
{
   switch($var)
   {
   case "blah":
     //do this
   break;
   case "blahblah":
    //do this instead
   break;
   default:
     //do this if no case is true
   }
}
else
{
   $err = 'Blah blah...';
}

[snorky]

I'm getting the variables from the database:

while($row=mysql_fetch_array($rpt1))

{

    $id=      $row["id"];

    $lname=  $row["lname"];

    $fname= $row["fname"];

    $emdiff= $row["emdiff"];

}

Within the context of what you said, are those variables "set"?

 

I've never used  isSet(), and I've never had problems with switch statements before. But I've never used NULL and NOT NULL before, either.

 

Back to the original question, 

In a switch statement, how do I form the cases to account for

    * an empty field

    * a non-empty field whose value is NULL

    * a non-empty field whose value is NOT NULL

 

For an empty field,

case "": 

usually works OK, but the exact syntax for NULL and NOT NULL elude me.

[thebadbad]

Yep, your (understanding of the) syntax is wrong. You can actually rearrange the cases and add a default to achieve what you want:

 

<?php
switch ($emdiff) {
case '':
	// emdiff is blank
	break;
case "NULL":
	// emdiff IS NULL
	break;
default:
	//emdiff is neither 'blank' nor "NULL"
}
?>

Or switch() on true.