This error is typically caused by a missing } used in PHP to denote content belonging to a WHILE, IF, or FOR loop.
You might accidentally comment out a } when you comment out a line of code. For example:
while (x==y){
do this;
do that;}
If you decide you no longer want to "do that", be very careful to not remove the } as I have done here.
while (x==y){
do this;
//do that;}
Instead, it is better practice to keep } on its own line.
while (x==y){
do this;
//do that;
}