[New to Arrays]

Hi I am new to PHP (a week and a half now) and I am just beginning to read about arrays. I understand simple arrays, associative arrays, and multidimensional arrays also. The book I am reading explains the array types in an easy to understand way but the example programs they show at the end of the chapter are pretty confusing. They seem to get advanced when combining arrays with for and while loops.

 

So my questions is, is there a good source out there to learning and dealing with arrays? It does not matter to me if it is a book, online, or in any other form. Also, are arrays very important to know when it comes to PHP?

 

Thanks in advance for your time and answers.

[Need Help with PHP Logical Operator - Basic]

Hi, I am having a little trouble understanding this piece of code. I have only started reading about PHP a week ago and I am reading a book right now and I have been stuck for a day now on this. I have seen it in a bunch of examples but I am just confused on the ! Operator. Here is the code from the book.

 

<?php

// if form not yet submitted
// display form
if (!isset($_POST['submit'])) {

?>
<form method="post" action="primes.php"> 
Enter a list of numbers, separated by commas:
<br /> 
<input type="text" name="num" />
<p> <input type="submit" name="submit" value="Submit" />
</form>

 

I am having trouble with this line:

 

if (!isset($_POST['submit'])) {

 

Any help is greatly appreciated. Thanks