Marginally Clever

function test_form_X() {  // where X is the name of a form, in case there are multiple forms on the same page
  ok=true;
  msg='';
  first=1;
  $('#X .form_item').removeClass('error');  // jQuery/CSS magic!
 
  ...
  // let's assume we have a form element called form_element_N.
  if(is_form_element_N_ok()==false) {
    ok=false;
    msg+='Form element N is no good!\n';
    if(first) {
      form_element_N.focus();
      first=0;
    }
    // every input/select/textarea is inside an input_item inside a form_item.
    $('#form_element_N').parent.parent.addClass('error');  // jQuery/CSS magic!
  }
  ...
 
  if(ok==false) alert(msg);
  return ok;
}

function add_form_error($name,$message) {
  $str ="      if(first) {\n";
  $str.="        first=0;\n";
  $str.="        \$('#$name').focus();\n";
  $str.="      }\n";
  $str.="      \$('#$name').parent.parent.addClass('error');\n";
  $str.="      ok=false;\n";
  $str.="      msg+='".str_replace(array("'","\'"),$message)."';\n";
  return $str;
}

// Create a javascript error message for fields that can't be left blank.
function add_form_test_required($name,$label=null) {
  $test="    if(\$('$name').value==null || \$('$name').value.length==0) {\n"
       .add_form_error($name,"$label is required.\n")
       ."    }\n";
 
  add_form_test($test,$name);
}
 
function add_form_test($test,$name) {
  global $forms_to_validate,$last_form_name;
 
  $forms_to_validate[$last_form_name].=$test;
}
 
function create_form_start(name='form1',$classname='form',$action='',$method='post',$target='') {
  global $forms_to_validate,$last_form_name;
 
  $forms_to_validate[$name]='';
  $last_form_name=$name;
  return "
< form id="$name" class="$classname" action="$action" enctype="multipart/form-data" method="$method">\n";
}

function form_header() {
  global $forms_to_validate;
 
  echo "  <script type="'text/javascript'"><!--mce:0--></script>\n";
}

$body=create_form_start();
$body.=create_form_text('name','Name','','Your Name');
$body.=create_form_password('user_pass','Password','','Your Password. <a href="forgot.php">Did you forget your password?</a>');
$body.=create_form_required('name','Name');