Pagination not working in WP_Query() - php

Question

My pagination is not working with WP_Query().
I have a total of three posts. Page 1 correctly displays all three posts. But page 2 displays the same three posts. In fact, there should not be a page 2 since page 1 displays all three posts already.
What could be wrong?
.
Loop in index.php
<?php
$query = new WP_Query('cat=1');
if ($query->have_posts()) :
while ($query->have_posts()) : $query->the_post();
the_title();
endwhile;
endif;
?>
<?php my_pagination(); ?>
.
.
Pagination in functions.php
if ( ! function_exists( 'my_pagination' ) ) :
function my_pagination() {
global $wp_query;
$big = 999999999; // need an unlikely integer
echo paginate_links( array(
'base' => str_replace( $big, '%#%', esc_url( get_pagenum_link( $big ) ) ),
'format' => '?paged=%#%',
'current' => max( 1, get_query_var('paged') ),
'prev_next' => True,
'total' => $wp_query->max_num_pages
) );
}

Answer 1

Your query variable in your main loop is $query whereas your query variable in your pagination is $wp_query. Try using $query in place of $wp_query.
So for example:
if ( ! function_exists( 'my_pagination' ) ) :
function my_pagination() {
$big = 999999999; // need an unlikely integer
echo paginate_links( array(
'base' => str_replace( $big, '%#%', esc_url( get_pagenum_link( $big ) ) ),
'format' => '?paged=%#%',
'current' => max( 1, get_query_var('paged') ),
'prev_next' => True,
'total' => $query->max_num_pages
) );
}
Note: your code seems to be missing an endif;

Answer 2

Try with this code for your query:
global $wp_query;
$paged = get_query_var('paged') ? get_query_var('paged') : 1;
$wp_query = new WP_Query('cat=1&paged=' . $paged);
if ($wp_query->have_posts()) :
while ($wp_query->have_posts()) : $wp_query->the_post();
the_title();
endwhile;
endif;
my_pagination();
In case it still does not work (that might happen depending on the context), try replacing:
$paged = get_query_var('paged') ? get_query_var('paged') : 1;
with
$paged = get_query_var('page') ? get_query_var('page') : 1;