Insert multiples values in the value of the checkbox

What I want is to insert multiple values in the value of my checkbox and send it to my function myAlert(this) in only one String like "code_dateAdded_..."

echo '<td><input type="checkbox"  onclick="myAlert(this)" name="code" id="code" value="'.$donnees['code'].'_'.$donnees['dateAdded'].'"/>'.$donnees['code'].'</td>';

the value should be like this value="355422_2015-07-30 03:00:16"

I tried to insert like that but when I do an echo on my value I only get the value of $donnees['code'] and not following values like the underscore and the following value $donnees['dateAdded']

Is it possible to do like this and if not how can I do it

Thanks