Umwandlung von Arrays und Zeichenketten

Array
(
    [0] => HTML
    [1] => CSS
    [2] => JavaScript
    [3] => ActionScript
    [4] => PHP
)

HTML, CSS, JavaScript, ActionScript, PHP

Array
(
    [0] => HTML
    [1] => CSS
    [2] => JavaScript
    [3] => ActionScript
    [4] => PHP
)