Question

I’m modifying a wordpress template and I’m curious as to how this is a valid control structure in PHP. Anyone have any insight?

<?php if(condition): ?>
<?php if(!condition || !function()) ?>
<?php elseif(condition): ?>
<?php if(!condition || !function()) ?>
<?php endif; ?>

If I remove all the tags, I get (with more sane indentation):

<?php
if(condition):
    if(!condition || !function())
elseif(condition):
    if(!condition || !function())
endif;
?>

which is invalid because the indented if statements don’t end. So how/why is this code valid if there are opening and closing php tags everywhere?

---

Edit for Kerrek SB. Make a php file and run it. It’s valid:

<?php if(true): ?>
<?php if(true) ?>
<?php endif; ?>
<?php echo 'here'; ?>

Answer 1

Your (reduced) example code is equivalent to this:

<?php
if(condition):
    if(!condition || !function()) { }
endif;
?>

Or even:

<?php
if(condition):
    if(!condition || !function());
endif;
?>

By closing off the <?php tag, you appear to get an “empty statement” for free.

Your real example could be one-lined like so:

<?php if(true): if(true); endif; echo 'here'; ?>

But note that an elseif makes this ambigous!

<?php
if(condition):
    if(!condition || !function());
elseif(condition):   // Bogus! which block does this belong to?
    if(!condition || !function());
endif;
?>

We’d have to disambiguate this:

<?php
if(condition):
{
    if(!condition || !function());
}
elseif(condition):
{
    if(!condition || !function());
}
endif;
?>

Now it’s clear, but now we could have spared ourselves the colon syntax altogether.

Thanks to Lekensteyn for pointing this out!

See the discussion below for further oddities.