How to get first post page in a paginated post with

There is a global $pages variable that contains the content of the page as an array of each page.

So inside the loop:

global $pages;
$first_page = $pages[0];

To get the first page of a post with the id, say, 33, outside the loop, you can do:

global $post;
$post = get_post( 33 );
setup_postdata( $post );
global $pages;
$first_page = $pages[0];
wp_reset_postdata();

Edit: I believe I’ve misunderstood your question slightly.That’s how to get the first page, not determine the one you’re on. I think all you need is:

global $page;
if ( $page == 1 ) {
// Do something
}

Hi, thank you very much for your quick answer,

global $page;
if ( $page == 1 ) {
// Do something
}

$page in the first page returned 0 & for the second returned.
is it normal?!
for me the first page is $page==0,is it right?

sorry again for the english!

That code will only work inside the loop. (so after the_post(); and before endwhile;.

The good thing is that outside the loop it still picks up pages 2 & 3 and so on. So you just need to check:

global $page;
if ( $page == 1 || $page == 0 ) {
    // Do something
}

Only problem you might run into is if you want the first page of a multi-page page to look different to pages that only have one page. Since $page also equals zero when there are no pages.

You’d need to do something like this to account for that:

while( have_posts() ) : the_post();
    global $pages;
    $page_count = count( $pages );
endwhile;

global $page;

if ( $page_count > 1 && ( $page == 0 || $page == 1 ) ) {
    // First page of multi-page page
} else {
    // Page only has one page
}

sorry for answering to late,
thank you for the non paginated posts point and it did the trick.
it was really very helpful!