0:$a =  $b = 

1:$a = 9 $b = 4


0:$a = 9 $b = 4

1:$a = 3 $b = 4

2:$a = 8 $b = 4

3:$a = 8 $b = Hello 

4:$a = 8 $b = Hello There!

ARRAY OPERATORS:

array(2) {
  ["a"]=>
  string(5) "apple"
  ["b"]=>
  string(6) "banana"
}
array(3) {
  ["a"]=>
  string(4) "pear"
  ["b"]=>
  string(10) "strawberry"
  ["c"]=>
  string(6) "cherry"
}
Union of $a and $b: 
array(3) {
  ["a"]=>
  string(5) "apple"
  ["b"]=>
  string(6) "banana"
  ["c"]=>
  string(6) "cherry"
}
Union of $b and $a: 
array(3) {
  ["a"]=>
  string(4) "pear"
  ["b"]=>
  string(10) "strawberry"
  ["c"]=>
  string(6) "cherry"
}
Union of $a += $b: 
array(3) {
  ["a"]=>
  string(5) "apple"
  ["b"]=>
  string(6) "banana"
  ["c"]=>
  string(6) "cherry"
}