Enviar post e fazer upload de imagem do front-end

Se você está falando sobre a resposta que eu postei aqui é simplesmente fazer o upload de um arquivo em um iframe para obter o envio "Ajax like".

Agora, se você já tiver um formulário que lide com o envio de postagens, basta adicionar a entrada do campo do arquivo de upload em algum lugar em seu formulário:

<form ...
...
<input type="file" name="thumbnail" id="thumbnail">
...
...
</form>

certifique-se de que seu formulário tenha o atributo enctype="multipart/form-data" .

em seguida, no seu script de processamento de formulário depois de criar a postagem (supondo que você esteja usando wp_insert_post(); ) mantenha o ID do post em um novo var:

$new_post = wp_insert_post($post_array);

e depois disso, adicione:

            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, $new_post );
                }   
            }
            if ($attach_id > 0){
                //and if you want to set that image as Post  then use:
                update_post_meta($new_post,'_thumbnail_id',$attach_id);
            }

e sua imagem será carregada e salva como miniatura de postagem.

Marcação HTML:

 <p>
   <label for="custom-upload">Upload New Image:</label>
   <input type="file" tabindex="3" name="custom-upload" id="custom-upload" />
 </p>
 <?php
  /*Retrieving the image*/
  $attachment = get_post_meta($postid, 'custom_image');

  if($attachment[0]!='')
  {
   echo wp_get_attachment_link($attachment[0], 'thumbnail', false, false);
  }

 ?>

Fazendo o upload da imagem:

<?php
global $post; /*Global post object*/
$post_id = $post->ID; /*Geting current post id*/
$upload = $_FILES['upload']; /*Receive the uploaded image from form*/
add_custom_image($post_id, $upload); /*Call image uploader function*/

function add_custom_image($post_id, $upload)
{
 $uploads = wp_upload_dir(); /*Get path of upload dir of wordpress*/

 if (is_writable($uploads['path']))  /*Check if upload dir is writable*/
 {
  if ((!empty($upload['tmp_name'])))  /*Check if uploaded image is not empty*/
  {
   if ($upload['tmp_name'])   /*Check if image has been uploaded in temp directory*/
   {
    $file=handle_image_upload($upload); /*Call our custom function to ACTUALLY upload the image*/

    $attachment = array  /*Create attachment for our post*/
    (
      'post_mime_type' => $file['type'],  /*Type of attachment*/
      'post_parent' => $post_id,  /*Post id*/
    );

    $aid = wp_insert_attachment($attachment, $file['file'], $post_id);  /*Insert post attachment and return the attachment id*/
    $a = wp_generate_attachment_metadata($aid, $file['file'] );  /*Generate metadata for new attacment*/
    $prev_img = get_post_meta($post_id, 'custom_image');  /*Get previously uploaded image*/
    if(is_array($prev_img))
    {
     if($prev_img[0] != '')  /*If image exists*/
     {
      wp_delete_attachment($prev_img[0]);  /*Delete previous image*/
     }
    }
    update_post_meta($post_id, 'custom_image', $aid);  /*Save the attachment id in meta data*/

    if ( !is_wp_error($aid) ) 
    {
     wp_update_attachment_metadata($aid, wp_generate_attachment_metadata($aid, $file['file'] ) );  /*If there is no error, update the metadata of the newly uploaded image*/
    }
   }
  }
  else
  {
   echo 'Please upload the image.';
  }
 }
}

function handle_image_upload($upload)
{
 global $post;

        if (file_is_displayable_image( $upload['tmp_name'] )) /*Check if image*/
        {
            /*handle the uploaded file*/
            $overrides = array('test_form' => false);
            $file=wp_handle_upload($upload, $overrides);
        }
 return $file;
}
?>