PHP Operators

The reference operator & — the reference operator is mainly used in associative assignment. When one variable is assigned to another variable, a copy of the original variable is produced first, and then that copy is saved in memory.
For example: $a=1; $b=$a; echo $b; the result is 1
If $a=2; then echo $b; the result is still 1 .
Because the copy assigned to $a is still in memory, the assignment is still a copy of the first value. So we use the reference operator &, which resets the original address being pointed to.