Some other IDEs has this, and it is very useful in large projects.
Say you have 20 occurrence of $my_var in a page
When the cursor is in any of the $my_var instances, pressing CTRL+R (or any other combination) will highlight the variable and when you change it, all the instances will change.

There are quite a few cases I encountered that simple search/replace won't work.
Example:
Need to change $password to $passw, but I also have $password_plain, $password_encrypted. $password_new, $password_old etc. So search replace will change all of them.

regards.