[TYPO3] using checkbox values in srfeuserregister

[Jeroen Visser]

Hi,
I have extended the srfeuserregister form with a own extension for adding more field to the form.
The user must use check boxes to say what kind of magazine he would like to receive. This can be more than one.

After submitting the form the validation form only gives the first item of the checkbox array. My TCA for these checkboxes looks like:

"tx_myName" => Array (		
	"exclude" => 1,		
	"label" => "LLL:EXT:myExt/locallang_db.xml:fe_users.tx_myName",		
	"config" => Array (
		"type" => "check",
		"cols" => 4,
		"items" => Array (
			Array("LLL:EXT:myExt/locallang_db.xml:fe_users.tx_myName.I.0", ""),
			Array("LLL:EXT:myExt/locallang_db.xml:fe_users.tx_myName.I.1", ""),
			Array("LLL:EXT:myExt/locallang_db.xml:fe_users.tx_myName.I.2", ""),
			Array("LLL:EXT:myExt/locallang_db.xml:fe_users.tx_myName.I.3", ""),
			Array("LLL:EXT:myExt/locallang_db.xml:fe_users.tx_myName.I.4", ""),
			Array("LLL:EXT:myExt/locallang_db.xml:fe_users.tx_myName.I.5", ""),
		),
	)
),

In the constants I have tried:
plugin.tx_srfeuserregister_pi1.parseValues.tx_myName = multiple

No luck so far.

Maybe someone knwos what is missing here?
Thanks in advance.

Greetings,
Jeroen