How to use the value of a variable that is declared as an array ( ending with '[ ]' )?

<?php $postid[] = get_the_ID(); // capture the id (a number) ?>

Now If I echo $postid I just get: Arra开发者_开发知识库y

and when I do the following:

<?php
    $default = array(
        'posts_per_page' => $postid
    );
?>

I don't get anything either.

Any suggestions?

When working with arrays in PHP, you can use the following to assign an array to a variable :

// initalize empty array
$a = array();
var_dump($a);

(The array() could be non-empty, of course)

Or you can use the following syntax, without the indexes :

// push items at the end of the array
$a[] = 10;
$a[] = 20;
var_dump($a);

And, finally, you can set an item at a key of your choice :

// put an item at a given index
$a['test'] = 'plop';
var_dump($a);

For more informations, see the Arrays sections of the manual.

Doing so, thanks to the three var_dump() calls, I'll get :

array
  empty

array
  0 => int 10
  1 => int 20

array
  0 => int 10
  1 => int 20
  'test' => string 'plop' (length=4)

Note : many use print_r() instead of var_dump() -- I tend to prefer var_dump(), which displays more informations, especially when the Xdebug extension is installed.

But note that, in any case, calling echo on an array itself :

echo $a;

Will get nothing else as output than :

Array

Which is not quite useful ;-)

Still, you can display the value of a single item of that array :

echo $a['test'];

Which, in this case, would get you this output :

plop

Basically : echo is not what you should use when you want to display an array :

• Either use var_dump() if you want to inspect an array for debugging purposes,
• or loop over the array with foreach, displaying each item with echo
  • Note : you might have to do some recursion, to inspect sub-arrays ;-)