String Splitting in PHP

Задание 1

Given a string:

php<?php
  $str = 'aaa bbb ccc';
?>

Write each word of this string into a separate array element.

Задание 2

Given an array:

php<?php
  $arr = ['a', 'b', 'c', 'd', 'e'];
?>

Merge the elements of this array into a string so that they are separated by commas.

Задание 3

Given a string:

php<?php
  $str = '1234567890';
?>

Split it into the following array:

php['12', '34', '56', '78', '90']

Задание 4

Given a string:

php<?php
  $str = '1234567890';
?>

Split it into the following array:

php['1', '2', '3', '4', '5', '6', '7', '8', '9', '0']

Задание 5

Given a string:

php<?php
  $str = '1234567890';
?>

Make the following string from it without using a loop:

php'12-34-56-78-90'

Задание 6

The variable $date contains a date in the format year-month-day. Convert this date to the format day.month.year.

Задание 7

Given a string:

php<?php
  $str = 'word※word※word※word';
?>

Split the string by the character '※' using mb_split.

Задание 8

Given a string:

php<?php
  $str = 'программирование';
?>

Split the string into an array of characters using mb_str_split.

Задание 9

Given a string:

php<?php
  $str = 'кириллица';
?>

Split the string into an array of characters using mb_str_split, specifying a fragment length of 2 characters.