no (variable or object)

Determine whether a variable or an object exist, i.e. were defined before in the code.

for (i=1,i<5,i++)

Programming a loop. Expressions can be separated by commas or by semicolon.

break

Ends execution of the current for, foreach, while, do-while or switch structure.

continue

Used within looping structures to skip the rest of the current loop iteration and continue execution at the condition evaluation and then the beginning of the next iteration.