Returns HTML for a textfield form element.
$variables: An associative array containing:
function theme_textfield($variables) {
$element = $variables['element'];
$element['#attributes']['type'] = 'text';
element_set_attributes($element, array(
'id',
'name',
'value',
'size',
'maxlength',
'placeholder',
));
_form_set_attributes($element, array(
'form-text',
));
return '<input' . new Attribute($element['#attributes']) . ' />' . drupal_render_children($element);
}