“Call to a member function have_posts() on array” error on have_posts();

Question

I'm having the weirdest error.

When trying to display a custom loop, I get the following error:

Fatal error
: Uncaught Error: Call to a member function have_posts() on array in /.../custom-page.php:42 Stack trace: #0 /.../wp-includes/template-loader.php(106): include() #1 /.../wp-blog-header.php(19): require_once('/data/sites/web...') #2 /.../index.php(17): require('/data/sites/web...') #3 {main} thrown in
/.../custom-page.php
on line
42

Which is so weird, because I've seen the error with 'call to a member function on null' or something else, but not on array, which is usually fine for this function.

The content of my custom-page.php has something like this:

<?php get_header(); ?>

<div class="container">
    <div class="row">
        <div class="col-12">
            <h1><?php the_title(); ?></h1>
            
            <div class="grid row">
                
                <?php foreach( $programs as $program ) {
                    
                    $custom_query = get_posts( [
                        'post_type'=> 'artikel',
                        'post_status' => 'publish',
                        'posts_per_page' => 1,
                        'order' => 'DESC',
                        'orderby' => 'date',
                        'meta_query' => [
                            [ 'key' => 'layout', 'value' => 'synopsis' ],
                            [ 'key' => 'programs', 'value' => '"' . $program . '"', 'compare' => 'LIKE' ]
                            ]
                        ] );
                    
                    if( $custom_query->have_posts() ) {
                        
                        echo 'test';
                        
                    }
                    
                } ?>
                
            </div>
            
        </div>
    </div>
</div>

<?php get_footer(); ?>

Answer 1

Well, get_posts() returns an array, so you probably (made a typo and) meant to use new WP_Query there:

get_posts() returns an array of, by default, post objects (see WP_Post), and arrays do not have methods (functions in a PHP class), hence you can't use the "arrow" on an array variable, and so that explains the error "Call to a member function have_posts() on array".

$array = array( 1, 2, 3 );
$array->foo(); // error - $array is an array, not an object

class MyClass {
    public function foo() {
        echo 'it works';
    }
}
$object = new MyClass;
$object->foo(); // works - $object is an object (or a class instance) and the
                // method foo() exists and callable/public

And the have_posts() in question belongs in the WP_Query class, so you may want to do $custom_query = new WP_Query( [ <args> ] ) and not $custom_query = get_posts():

$custom_query = new WP_Query( [
    // your args here
] );

I hope that helps, and if you need further help with WP_Query, check out the documentation.