Testing to see if table field is empty

[zeusofolus]

I know you can use the if/elseif to make php compare values

if ( $Quantity != 0){
	 $a = ( $b * $c );
	 
		}
elseif ( $Quantity == 0){ 

$a = ( $b + $c );
	 
		}

but what if you want it to do something only if a field has no value.

if ( $Quantity != ' '){
	 $a = ( $b * $c );
	 
		}
elseif ( $Quantity == 'all other values'){ 

$a = ( $b + $c );
	 
		}

[noelthefish]

if(!$variable)
{
}

[almostbob]

as noelthefish wrote, the elseif is redundant and takes (miniscule) resources to run, the ! means not,
If (not$variable) {do something;}
else {do something else}

[zeusofolus]

Great! This works

Thanks for the input.

Eric