正确的If语句使用方法

Question

Need help understanding proper way of using "if elseif else" statements. CODE A below works but is it correct? Am I allowed to end the statement with "elseif"? Or are "if" statements supposed to end with either "endif" or "else" ?

CODE A: This code works

But notice it does not end with "endif" or "else".

if ( is_page( 'contact' ) ) { get_template_part('inc/contact'); }
elseif ( is_page( 'policy' ) ) { get_template_part('inc/policy'); }
elseif ( is_page( 'about' ) ) { get_template_part('inc/about'); }
elseif ( is_page( 'terms' ) ) { get_template_part('inc/terms'); } 
?>

.
Are all "if statements" supposed to end with "endif"? If yes, can you show me the code? In CODE B below using "endif" results in White Screen error.

CODE B: endif does NOT work

if ( is_page( 'contact' ) ) { get_template_part('inc/contact'); }
elseif ( is_page( 'policy' ) ) { get_template_part('inc/policy'); }
elseif ( is_page( 'about' ) ) { get_template_part('inc/about'); }
elseif ( is_page( 'terms' ) ) { get_template_part('inc/terms'); } 
endif;
?>

.
Is the last "elseif" supposed to be "else" instead? If yes, can you show me the code? In CODE C below using "else" results in White Screen error.

CODE C: "else" instead of "elseif" does NOT work

if ( is_page( 'contact' ) ) { get_template_part('inc/contact'); }
elseif ( is_page( 'policy' ) ) { get_template_part('inc/policy'); }
elseif ( is_page( 'about' ) ) { get_template_part('inc/about'); }
else ( is_page( 'terms' ) ) { get_template_part('inc/terms'); }
?>

Answer 1

The endif is only used with the "alternate syntax" http://php.net/manual/en/control-structures.alternative-syntax.php personally i wouldn't use it, but its up to you.

per your "else" question .. it is optional. its the "failsafe" ... if nothing else matches then it is executed. if you don't have an "else" and all of your elseif's fail, then nothing will be done in that code block.

Answer 2

You can make use of : and endif OR curly brackets ( {} ), but not both. Either of these syntaxes will work

if( something_is() ) :
  do something;
endif;

or

if( something_is() ) {
  do something;
}

The second is actually the prefered way as it is easier to debug as nearly all code editors support this syntax. The first is quite hard to debug as it is not supported by most of the code editors

Answer 3

people tend to use this syntax in php-based templates, because it kinda looks template-ish

   <? if (something) : ?>
    <b>Yea!</b>
    <? else: ?>
    <p>nothing</p>
    <? endif; ?>

as for backend stuff its recommended to use this syntax

if (something) { bar(); } 
elseif (other)
{
  yes();
}
?>

php also allows this

if (something) myThing() elseif (that) other(); else doNot();

bottom line, you can only combine one type of syntax

Answer 4

I would say Code A. else is used when you want to say:

if(/*option;*/)
{
//code
}
elseif(/*another option;*/)
{
//code
}else /*Any other options beside the above*/ {/*code;*/}

But in your code you have a special case in the last condition. So CodeA.