I’m trying to filter product with ajax and when i sent data to ajax function

it’s Shows Error in output as Warning: urlencode() expects parameter 1 to be string, array given in C:\Users\Loha\Sites\wordpress.dev.cc\wp-includes\formatting.php on line 5501

this is my code:

if(!empty( $_POST['product_cat'] )){
  $args['tax_query'][] = array(
      'taxonomy'  => 'product_cat',
      'field'  => 'term_id',
      'terms'  => $_POST['product_cat'],
  );
}