PHP Taskbook Level 2.10
Given a string of letters and numbers, check that there are no more than three letters in this string.
Given a number, get the first even digit from the end of this number.
Given a string:
'abcde abcde abcde'
Replace the first character of each word in it with '!':
'!bcde !bcde !bcde'
Given an array of numbers:
[1, 2, 3, 3, 4, 5]
Check that this array contains two identical elements in a row.
