Simple "== x OR y" in PHP - php

Question

I have a loop in which I check for numbers. Something like this, more or less:
<?php $counter = 0; ?>
<?php /* The loop */ ?>
<?php while ( have_posts() ) : the_post(); ?>
<?php $counter++; ?>
<?php get_template_part( 'content', get_post_format() ); ?>
<?php if ($counter == (2 || 4)) : ?>
// DO SOMETHING
<?php endif; // counter ?>
...
But $counter ==(2||4) returns true for every number (1, 2, 3, 4 etc.). I also tried:
$counter == 2 || 4
$counter === 2 || 4
$counter == (2 or 4)
But to no avail. The first and last one also return true for every natural number and the second one never returns true.

Answer 1

An alternate solution would be to do the following:
$allowed = array(2, 4);
if (in_array($counter, $allowed)) {
// good value
}
The advantage of this is that you can extend the list of allowed values very easily, maybe even placing them in an external config.

Answer 2

simply replace
if ($counter == (2 || 4)) :
with
if ($counter == 2 || $counter == 4) :
see also the manual: http://www.php.net/manual/en/control-structures.if.php

Answer 3

If you want to do something when the counter is even, you can use the following:
<?php if ($counter % 2 === 0) : ?>
// do something
// will match 0, 2, 4, 6, ...
<?php endif; ?>

Answer 4

Its not possible to check for multiple values inside a condition like that.
This is one reason why php sucks... you're are forced to use two conditions, like
if($counter == 2 || $counter == 4)
or if you want to trigger your conditions on even numbers
if($counter % 2 == 0)
someone mentioned in_array() but you should know that arrays are very expensive in php in terms of resources.

Answer 5

The expression (2 || 4) will always return true. This is because both operands to the || operator are non zero valued constants. It is essentially equivalent to (true || true) which is always true as is (false || true).
the expression
$counter == (2 || 4)
will yield true except when $counter is 0
You want to write
($counter === 2 || $counter === 4)
note that you should always use === instead of == because the latter performs type coercion on its operands.