PHP Taskbook Level 2.7

Задание 1

Given a string:

php'a bc def ghij'

Convert all substrings with less than or equal to three letters to uppercase. In our case, we should get the following:

php'A BC DEF ghij'

Задание 2

Given a symbol, find out whether this symbol is uppercase or lowercase.

Задание 3

Given a certain number, for example, this one:

php123789

Remove all odd digits from this number. In our case, we get the following result:

php28