Can someone explain the parentheses structure for negation operators

[probsdorg]

Can someone help me understand parentheses structure?

 

Why here does the second empty() have no parentheses before it and an extra parentheses at the end?

 

if (empty($subject) && empty($text)) {

....

 

And here, why is there an extra parentheses at the end?

 

if (empty($subject) && (!empty($text))) {

...

 

And here, why double parentheses in the 1st empty() and none before the 2nd empty() ?

 

if ((!empty($subject)) && empty($text)) {

...

 

Thank You! 

 

michael

[BlueSkyIS]

there must always be the same number of left parentheses as right parentheses. the far left and far right parentheses define the entire if statement. similarly, pairs of left/right parentheses can define sub-statements within the larger statement. also, a function called with a parameter must use () to pass that parameter. it might help you to understand if you either add more spaces between paren's and/or break them onto lines:

 

 

if (  empty($subject) && empty($text)) { // if $subject and $text are both emptyif (    empty($subject) && (!empty($text))) { // If $subject is empty and $text is not empty.// This is exactly the same without the extra paren's:if (    empty($subject) && !empty($text)) { // If $subject is empty and $text is not empty.

 

[KevinM1]

Moreover, parentheses enforce associativity.  If the order of operations of an expression aren't known, extra parentheses can be used to explicitly enforce a particular ordering.  http://www.php.net/manual/en/language.operators.precedence.php