PHP if not equal(!=) and or (||) issue. Why doesnt this work?

Question

I know this is simple PHP logic but it just won\'t work...

 $str = \"dan\";
 if(($str != \"joe\") 
   || ($str != \"danielle\")
   || ($str != \"heather\")
          


        

Answer 1

Welcome to boolean logic:

$str = 'dan'

$str != "joe" -> TRUE, dan is not joe
$str != "danielle" -> TRUE, danielle is not dan
$str != "heather") -> TRUE, heather is not dan
$str != "laurie" -> TRUE, laurie is not dan
$str != "dan" -> FALSE, dan is dan

Boolean logic truth tables look like this:

and:

TRUE && TRUE -> TRUE
TRUE && FALSE -> FALSE
FALSE && FALSE -> FALSE
FALSE && TRUE -> FALSE

or:

TRUE || TRUE -> TRUE
TRUE || FALSE -> TRUE
FALSE || TRUE -> TRUE
FALSE || FALSE -> FALSE

Your statement boiled down to:

TRUE || TRUE || TRUE || TRUE || FALSE -> TRUE