get_comments not working consistantly with post_id

Question

I am trying to get comments from another post. I am getting the post_id and doing a check to see if it has comments

I can get the comments for the current post every time but for the other post I am getting mixed results (I did get it working but am unable to reproduce the results)

This is the code I'm working on with some alternate attempts commented out:

if(get_comments_number($getLangsPostID) > 0){
    //echo "<pre>This post id is ".$thisPostID." The other language post id is (".$getLangsPostID."):";
    //var_dump($getLangsPostID);
    $altLangReq = array(
        'post_id' => $getLangsPostID // have tried with and without trailing comma
    );

    //$langComments = get_comments($altLangReq);
    $langComments = get_comments('post_id='.$getLangsPostID);

    echo "<p>Current post ($thisPostID), request for post id (".$getLangsPostID.") is:<pre>";
    var_dump($langComments);
    //$x = get_comments('post_id=31'); // hard coded also fails
    $x = get_comments(array('post_id'=>31));
    var_dump($x);
    echo "</pre></p>";

If it matters I am using polylang and trying to show comments from all language alternatives on each languages post. I am using two posts (id 21 and 31) which have 3 or 4 comments each (these are getting found by get_comments_number.

Also I am outside the comment loop on the comments.php template in slightly customised underscore theme.

Edit:

Some clarification, I wanted to describe most of the conditions incase there was some other factor but basically if I call:

var_dump(get_comments('post_id=21')); // 21 is the current post

I get the current posts comments, if I call:

var_dump(get_comments('post_id=31')); // 31 is a different post

I get an empty array, if I go to post 31, then 31 works and 21 returns an empty array but this seems to be the way to call posts other than the current one (via the post_id). See the first example in the WP codex

Edit 2 Answer: (I am adding this for now as I am not able to answer my own question for 8 hours ATM)

Turns out it was the language plugin... When I call the comments it adds a language filter:

'lang' => $currentLang

So I had to explicitly override that:

get_comments(array('post_id'=>31, 'lang' => $targetLang));

I still don't know why I was sometimes able to get the other comments without this.

Answer 1

Turns out it was my use of the language plugin (polylang)... When I call the comments it adds a language filter:

'lang' => $currentLang

So I had to explicitly override that:

get_comments(array('post_id'=>31, 'lang' => $targetLang));

I still don't know why I was sometimes able to get the other comments without this.

Answer 2

The post must be have a comment.

$comments = get_comments( array( 'post_id' => $id ) );

if( empty( $comments ) ) {
    return;
}

foreach( $comments as $val ) { 
   echo $val->comment_content;
}