substitute for assigning with array()?

I had some code that was working nicely. In it, I was assigning values to a multidimensional array like: $array_name[0] = array( key1 => 'val', key2 => 'val', key3 => 'val'); I added a function that directly assigns vars to the same array like: $array_name[0][key4] = 'val'; If this function is called prior to the multiple assignment code, it erases the directly assigned key/value pair [key4] = 'val'. So I have to change my original code to do direct assignment. !! definitely is more difficult to read and doesn't look as neat. Is there an alternative I haven't thought about? Thanks