# CodeStepByStep

## count_to_by

Language/Type: PHP recursion

Write a recursive function named `count_to_by` that accepts integer parameters `\$n` and `\$m` and that produces output indicating how to count to `\$n` in increments of `\$m` separated by commas. For example, to count to 10 by 1 you'd say `count_to_by(10, 1);` The following table shows several other calls and their expected output:

Call Meaning Output
`count_to_by(10,1);` count to 10 by 1s `1, 2, 3, 4, 5, 6, 7, 8, 9, 10`
`count_to_by(25,4);` count to 25 by 4s `1, 5, 9, 13, 17, 21, 25`
`count_to_by(30,4);` count to 30 by 4s `2, 6, 10, 14, 18, 22, 26, 30`
`count_to_by(34,5);` count to 34 by 5s `4, 9, 14, 19, 24, 29, 34`
`count_to_by(3,6);` count to 3 by 6s `3`
`count_to_by(17,3);` count to 17 by 3s `2, 5, 8, 11, 14, 17`

Notice that the increment does not have to be 1, such as when counting to 25 by 4s. The count must always end at `\$n`, but notice that at will not always be possible to start counting at 1, as shown in the output when `\$n` is 30 and `\$m` is 4. But the first number should always be in the range of 1 to `\$m` inclusive. It is possible that only one number will be printed, as shown in the output when `\$n` is 3 and `\$m` is 6.

Your function should throw an `Exception` if either `\$m` or `\$n` is less than 1. Note that the output does not advance to the next line.

Function: Write a PHP function as described, not a complete program.