passing an array to wsdl file using php doesn't work properly

I have an array defined in in my client.php:

$array = array(13,"Maria","Mueller");

I pass it using $result1 = $client->__soapCall("function", array($array)); to the wsdl file.

in my wsdl it is written:

            <xsd:complexType name='function'>
                    <xsd:element name='item' type='xsd:string' maxOccurs='unbounded'/>

I think my wsdl is not working properly. I don't understand why it works, even if one of the values in the array is an integer value. I also use simple types and when I pass e.g. an Integer value to an element that is defines as string, its not working. Now I want, that it is also not working with my integer 13 in the array when I define that everything should be a string. Because I also have arrays that are only allowed to include integers and my wsdl should not pass that arrays when a string value occurs in this arrays.