ZF2 - Form creation missing validators - zend-framework2

Question

I am having a little trouble adding validators to a ZF2 form object. I an building a form from a schema set in a database so I can validate a set of user input quickly.
This is the code that generates the form object
//initialise the form
$form = new Form();
//need to loop through the schema to create the form
for($i=0; $i < count($schema); $i++)
{
$form_options = array();
//add the basics to the form
$form_options['name'] = $schema[$i]['field_name'];
$form_options['type'] = $schema[$i]['field_type'];
//check if this is a required field
if($schema[$i]['is_required'] == 'true')
{
$form_options['required'] = true;
}
//add functions to filter the input form
$function_filters = explode(',', $schema[$i]['function_filter']);
if(!empty($function_filters))
{
$filters = array();
for($j=0; $j < count($function_filters); $j++)
{
$filters = array('name' => $function_filters[$j]);
}
$form_options['filters'] = $filters;
}
//add validators to the field array
$validators = array();
if(!is_null($schema[$i]['min_length']) && !is_null($schema[$i]['max_length']))
{
$validators[] = array(
'name' => 'StringLength',
'options' => array(
'encoding' => 'UTF-8',
'min' => (int) $schema[$i]['min_length'],
'max' => (int) $schema[$i]['max_length'],
)
);
}
//our regex validator if it exists
if(!is_null($schema[$i]['regex_filter']) || strlen($schema[$i]['regex_filter']) != 0)
{
$validators[] = array(
'name' => 'regex',
'options' => array(
'pattern' => $schema[$i]['regex_filter'],
'messages' => array(
\Zend\Validator\Regex::INVALID => $schema[$i]['regex_invalid'],
\Zend\Validator\Regex::NOT_MATCH => $schema[$i]['regex_not_match'],
\Zend\Validator\Regex::ERROROUS => $schema[$i]['regex_errorus'],
)
)
);
}
//only add the validators if theres something in there
if(!empty($validators))
{
$form_options['validators'] = $validators;
}
$form->add($form_options);
}
//return our form object
return $form;
The block of code behaves the way I expect it, the output of $form_option after it's performed the above code looks like this:-
Array
(
[name] => username
[type] => Text
[required] => 1
[filters] => Array
(
[name] => StripTags
)
[validators] => Array
(
[0] => Array
(
[name] => StringLength
[options] => Array
(
[encoding] => UTF-8
[min] => 3
[max] => 50
)
)
[1] => Array
(
[name] => regex
[options] => Array
(
[pattern] => /^[a-zA-Z0-9_]{3,50}$/
[messages] => Array
(
[regexInvalid] => L_REGEX_INVALID
[regexNotMatch] => L_REGEX_USERNAME
[regexErrorous] => L_REGEX_ERRORUS
)
)
)
)
)
When I came to test it, it ignores the StringLength & Regex validators entirely, and only pay attention to the required validator for the last form element.
Anyone have any idea what's gone wrong?