Insert an image into a post by API

By using the code below, I can create a new post and upload an image to wordpress’s upload directory as a attachment through a form’s submitted data.

    $new_post = array(
        'post_title' => $title,
        'post_content' => $content,
        'post_status' => 'publish',
        'post_date' => date('Y-m-d H:i:s'),
        'post_author' => $user_ID,
        'post_type' => 'post',
        'post_category' => array(3)
    );
    $post_id = wp_insert_post($new_post);

    if (!function_exists('wp_generate_attachment_metadata')){
        require_once(ABSPATH . "wp-admin" . '/includes/image.php');
        require_once(ABSPATH . "wp-admin" . '/includes/file.php');
        require_once(ABSPATH . "wp-admin" . '/includes/media.php');
    }
    if ($_FILES) {
        foreach ($_FILES as $file => $array) {
            if ($_FILES[$file]['error'] !== UPLOAD_ERR_OK) {
                return "upload error : " . $_FILES[$file]['error'];
            }
            $attach_id = media_handle_upload( $file, $post_id );
        }   
    }

I want to insert an image to post, not replace the featured image so set_post_thumbnail() function is not appropriate. I found that if I manually insert an image to post, it will generated the HTML code likes:

<a href="http://192.168.1.12/wp/wp-content/uploads/2012/09/H530U_08.jpg"><img class="alignnone size-medium wp-image-136" title="HARP_SH530U_0" src="https://192.168.1.12/wp/wp-content/uploads/2012/09/HARP_SH530U_08-300x167.jpg" alt="" width="300" height="167" /></a>

So which API would provide the function of inserting image to post, likes generating the HTML code above and not replacing the featured image?

Thanks

You can set the uploaded image as the post thumbnail via,

update_post_meta($post_id,'_thumbnail_id',$attach_id);

Example…

if ($_FILES) {
    foreach ($_FILES as $file => $array) {
        if ($_FILES[$file]['error'] !== UPLOAD_ERR_OK) {
            return "upload error : " . $_FILES[$file]['error'];
        }
        $attach_id = media_handle_upload( $file, $post_id );
    }   
}

update_post_meta($post_id,'_thumbnail_id',$attach_id);

If you are uploading an array of images, then you might wish to specify which image by referencing the key,

$file[0] //for the first image in the array
$file[1] //for the second image in the array
$file[2] //for the third image in the array
etc...

…but that should not be necessary when uploading a single image.

Update:

Based on your comments, if you want to insert the image at the beggining of or before your post content its probably best you filter the the_content function like so,

add_filter( 'the_content', 'insert_img_to_post', 20 );

function insert_img_to_post( $content ) {

    global $post;
    $post_id = $post->ID;

    if ( is_single() )

        $content = sprintf(
            '<img class="post-icon" src="%s" alt="Post icon" title=""/>',
            wp_get_attachment_url(get_post_meta( $post_id, '_thumbnail_id', true )),
            $content
        );

    return $content;
}

…add this function as a separate function/filter in your functions.php file. Do not try and bundle it within your wp_insert_post function as it will not work. This is intended to run by itself, hooking onto the_content filter, inserting the image at the top of the post before the content, then appending the content beneath it.

This is currently running on a single post page (is_single) if you want it to run on something else, like a page, then change to is_page or any other conditional tag that meets your needs.