Yup, that's the correct way, but by using new, it blanks out all the values so you don't need to set them:
PHP Code:
new String:myArr[64][40];
// If you wanted define some values
new String:myArr[][] =
{
"first string",
"second string"
};
This creates 64 strings, each with a 40 character limit. To read one of them, we would do:
PHP Code:
PrintToServer("The value is: %s", myArr[0]);