title: Data not inserted but have no error PHP using bind_param
body: <p>i have a simple code to input data to my database 
  using prepare and bind_param</p>
  
  <p>there is no error but my data are not inputted into database </p>
  
  <pre><code>  $stmt1 = $mysqli -&gt; prepare ("INSERT INTO equipment(eqp_type, eqp_name, eqp_qty, eqp_usd, $eqp_idr) VALUES (?,?,?,?,?)");
    $stmt1-&gt;bind_param('sssss',$eqp_type, $eqp_name, $eqp_qty, $eqp_usd, eqp_idr);
    $eqp_type = 'BUC';
    $eqp_name = 'BUC test';
    $eqp_qty = '1';
    $eqp_usd = '0';
    $eqp_idr = '0';
    $stmt1-&gt;execute();
  </code></pre>
  
  <p>is there any idea why there is no error but my data are not inputted into database ?</p>