Wordpress - retrieving all top images from a post

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<?php
$servername = "localhost";
$username = "xxx";
$password = "xxx";
$dbname = "xxxx";


// Create connection

$conn = new mysqli($servername, $username, $password, $dbname);
mysqli_set_charset($conn, "utf8");
// Check connection
if ($conn->connect_error) {
die("Connection failed: " . $conn->connect_error);
}
// output data of each row
foreach ($conn->query('SELECT ID, post_date, post_title, post_type, post_name, guid FROM nyk3_posts WHERE post_type = "post" ORDER BY ID ASC') as $row){
echo "<b>ID: </b>".$row["ID"]." - <b>TÍTULO: </b><a data-toggle='lightbox' rel='modal' href='".$row["guid"]."' target='_blank'>". $row["post_title"]."</a> - <b>DATA: </b>". $row["post_date"];
echo "<br>";

  foreach ($conn->query('SELECT ID, post_parent,guid FROM nyk3_posts WHERE post_type = "attachment"') as $row2){

if ($row2["post_parent"] == $row["ID"]) {
        foreach ($conn->query('SELECT post_id,meta_value, meta_key FROM nyk3_postmeta WHERE meta_key = "_thumbnail_id"') as $row3)
          if ($row3["meta_value"] == $row2["ID"]) {
                foreach ($conn->query('SELECT post_id,meta_value, meta_key FROM nyk3_postmeta WHERE meta_key = "_wp_attached_file"') as $row4){
                 if ($row4["post_id"] == $row3["meta_value"]) {
                 echo  "<a data-toggle='lightbox' rel='modal' href='wp-content/uploads/".$row4["meta_value"]."' target='_blank'>".$row4["meta_value"]."</a><br><br>";
                }

         }
}
}
}


}


$conn->close();
?>
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