Post content not showing some content

Question

I'm inserting posts by wp_insert_post function. It works like first a post is created to get its id then an image is attached to that post id. I attach images by media sideload function. Here is the whole code module on which I'm working on :HERE . Initially post content is left blank.

$new_post = array(
    'post_title' => $title,   
    'comment_status' => 'open',
    'post_name' => $slug,
    'post_content' => '',
    'post_status' => 'draft',
    'post_date' => date('Y-m-d H:i:s'),
    'post_author' => 2,
    'post_type' => 'post',
    'post_category' => $cat_ids
    );
    $post_id = wp_insert_post($new_post);

When images is uploaded and attached after that I add a variable $content as below and update the post.

$content = $link[$i].'<br>'.'<img src="'.$src.'" alt="'.$img_title.'" title="'.$img_title.'" class="alignnone size-full wp-image-'.$img_id.'" width="500"/>';

$link[$i] contains the original url of that image. 
$src = wp_get_attachment_url( $img_id );

Everything works fine but problem is when I see the same post in the editor, it only shows as url of image. Rest is not displayed. I tried these:

1. Changed theme if css posing that problem. Result was same content was displayed as above url and no image tags in post editor.

2. I changed the code after <br>, as '1234 qwe asd zdc'. Resulted as url1234 qwe asd zdc <br> doesn't seem to work. There was no break.

3. Echoed direct $content variable without changing anything, on a blank file.php, displayed url and image correctly.

How to resolve this thing? I have been trying this for whole day but no success.

UPDATE: What I have found is probably, the post is updating but not taking new content in line 52 :here

Answer 1

If you do $content = "something"; you are replacing the $content variable's value. If you want to append something to the current content, you'd need to do something like:

$content = 'initial content';
$content .= 'more content (notice the dot)';

In this case, if you want to append the image to some existing content you'd need to do:

$content = get_the_content(); //or wherever the existing content is
$content .= $link[$i].'<br><img src="'.$src.'" alt="'.$img_title.'" title="'.$img_title.'" class="alignnone size-full wp-image-'.$img_id.'" width="500"/>';

Or the reverse if you want to put the image first, before any content.