Store loop into array

Question

I am using folowing code to store posts ids into array:

<?php
    $args = array(
        'post_type' => 'product',
        'post_status' => 'publish',
        'ignore_sticky_posts'   => 1,
        'posts_per_page' => 5,
        'orderby' => 'date',
        'order' => 'desc');
$id = array();
$counter = 1;       
$products = new WP_Query( $args );
if ( $products->have_posts() ) : while ( $products->have_posts() ) : $products->the_post();
    $id[$counter] = get_the_id();
    //custom_shop_array_create($product, $counter);
    $counter++;
endwhile;
endif;
?>

However it doesnt work because if I put print_r($id) after endif it only prints id of last post. Where am I making mistake?

Thanks in forward

Answer 1

Try to replace

$id[$counter] = get_the_id();

with

array_push( $id, get_the_ID() );

to collect the post id's into the $id array.

Update:

If you also use $ids instead of $id:

    $args = array(
        'post_type' => 'product',
        'post_status' => 'publish',
        'ignore_sticky_posts'   => 1,
        'posts_per_page' => 5,
        'orderby' => 'date',
        'order' => 'desc');
$ids = array();
$products = new WP_Query( $args );
if ( $products->have_posts() ) : 
    while ( $products->have_posts() ) : $products->the_post();
       array_push( $ids, get_the_ID() );
    endwhile;
endif;

Answer 2

While @birgire's answer solves the problem, it does not explain it. $id[$counter] = get_the_id(); should work but in this case triggers a Warning that you cannot use a scalar value as an array. Why?

the_post runs setup_postdata, which sets $id to the post ID, overwriting your $id and turning it into an integer. You can see that by adding var_dump after the_post(), like this:

$products->the_post();
var_dump($id);

Beyond that, your code is overly complex. You don't need the counter (and if you did you already have $products->current_post) and you don't need any particular function to push items onto the array. All you really need to do is use a variable that WordPress isn't already using, which is what makes birgire's solution work.

$args = array(
  'post_type' => 'post',
  'post_status' => 'publish',
  'ignore_sticky_posts'   => 1,
  'posts_per_page' => 5,
  'orderby' => 'date',
  'order' => 'desc'
);

$ids = array();  
$products = new WP_Query( $args );
if ( $products->have_posts() ) : 
  while ( $products->have_posts() ) : 
    $products->the_post();
    $ids[] = $post->ID;
    //custom_shop_array_create($product, $counter);
  endwhile;
endif;