why get_post_meta is returning 0?

Question

I'm trying to show all the posts on a page with an audio player in it and for that I'm looping through posts in the following manner:

<?php

$posts = get_posts();
$ID;
foreach( $posts as $item)
{
 global $post;
 $post_id = $item->ID;
 $file_id = get_post_meta($post_id, 'sound_s', true);
 $file_url = wp_get_attachment_url( $file_id );
 $attr = array(
'src'      => $file_url,
'loop'     => '',
'autoplay' => '',
'preload'  => 'none'
    );
    echo wp_audio_shortcode( $attr );

    $ID = $file_id;
    var_dump($file_id);
}

?>

But trying to echo or var_dump $file_id is returning in null due to which my audio player can not be shown. And yeah there's no mistake in meta key and $post_id is also returning currect value. So please tell me why is this happening?

Answer 1

Please try below code and check if 'sound_s' key exists in the array or not

$file_id = get_post_meta($post_id);
echo "<pre>";
print_r( $file_id );
exit;

Answer 2

Have you try to change the third attributes of get_post_meta() to false

$file_id = get_post_meta($post_id, 'sound_s', false);

and then access your variable by

var_dump($file_id[0]);