Array of NULL:

Warning: Expected array for frame 0 in %s on line %d
string(9) "#0 {main}"

Array of empty array:
string(36) "#0 [internal function]: ()
#1 {main}"

Array of array of NULL values:

Warning: File name is not a string in %s on line %d

Warning: Value for class is not a string in %s on line %d

Warning: Value for type is not a string in %s on line %d

Warning: Value for function is not a string in %s on line %d

Warning: args element is not an array in %s on line %d
string(58) "#0 [unknown file]: [unknown][unknown][unknown]()
#1 {main}"