JSFiddle - React, Tailwind, and code Playground

HTML

<select class="form-control" id="shape" name="shape">
  <option value="">Choose:</option>
  <option value="a">a</option>
  <option value="b">b</option>
  <option value="c">c</option>
  <option value="d">d</option>
  <option value="e">e</option>
  <option value="f">f</option>
</select>

<select class="form-control" id="waist" name="waist">
  <option value="">Choose:</option>
  <option value="1">1</option>
  <option value="2">2</option>
  <option value="3">3</option>
</select>

JavaScript

var chg = false;
$('#shape, #waist').change(function(){
	if ($(this).val() == "") return false;
    if (!chg){
        chg=true;
    }else{
			if ( $('#shape').val()=="" || $('#waist').val()=="" ) return false;
        var myimg = $('#shape').val() + $('#waist').val();
		  
		  //Pretending to do AJAX (jsFiddle cannot do ajax...)
				alert('Fetching image: ' +myimg);
				$('body').append('<img src="http://placekitten.com/100/100" />')
				return false; //END demo here
		  //END Fake AJAX
		  
        $.ajax({
            type: 'post',
             url: 'my_second_php_file.php',
            data: 'myimg=' +myimg,
            success: function(d){
                //if (d.length) alert(d);
                $('#someDIV').html(d);
            }
        }); //END AJAX
    }//end else
}); //END select.change