Query Meta Data

<?php
// display error
ini_set('display_errors',1);
ini_set('display_startup_errors',1);
error_reporting(-1);
$con = dbconn();
if (!mysqli_connect_errno()) {

   echo 'connected';

   //Database Connection
   $query_exec = mysqli_query($con, "set names 'utf8'");
   $query_search = "
   SELECT
      p.post_title,
      p.post_date,
      usd_buy.meta_value AS 'USD Buy',
      usd_sell.meta_value AS 'USD Sell',
      thb_buy.meta_value AS 'THB Buy',
      thb_sell.meta_value AS 'THB Sell'
   FROM  pr65ac2015_posts p
   INNER JOIN  pr65ac2015_postmeta AS usd_buy ON usd_buy.post_id = p.ID
   INNER JOIN  pr65ac2015_postmeta AS usd_sell ON usd_sell.post_id = p.ID
   INNER JOIN  pr65ac2015_postmeta AS thb_buy ON thb_buy.post_id = p.ID
   INNER JOIN  pr65ac2015_postmeta AS thb_sell ON thb_buy.post_id = p.ID
   where
      p.post_type = 'exchange' AND
      p.post_status = 'publish' AND
      usd_buy.post_id = 'usd_buy' AND
      usd_sell.post_id = 'usd_sell' AND
      thb_buy.post_id = 'thb_buy' AND
      thb_sell.post_id = 'thb_sell'
";
   $query_exec = mysqli_query( $con, $query_search );
   if ( $query_exec ) {
      echo '1';
      $rowcount = mysqli_num_rows($query_exec);
      var_dump($rowcount);
      if( $rowcount > 0 ){
         echo '2';
         while ( $row = mysqli_fetch_assoc( $query_exec ) ) {
            $output[] = $row;
         }

         echo "json_encode";
         print( json_encode( $output, JSON_UNESCAPED_UNICODE ) ) ;
      } else {
         echo '1';
      }
   }
   mysqli_close( $con );
}
function dbconn() {
   $strHostName = "localhost"; // host
   $strDbName = "mywebsite"; // database name
   $strUserName = "root"; // database username
   $strPassword = ""; // database password
   return new mysqli($strHostName, $strUserName, $strPassword, $strDbName);
}
?>