associative vs indexed

Can someone Explain to me the diferences between associative and indexed arrays please.

Indexed arrays behave like vectors and associative arrays behave like hash tables.

Example of indexed array:

$array[0] = "Joe";
$array[1] = "John";
$array[2] = "Smith";

Example of associative array;

$array["MyFirstName"] = "Joe";
$array["MyMiddleName"] = "John";
$array["MyLastName"] = "Smith";

Here to get to the value of "Joe" you use its
key which is "MyFirstName".

Ok, thanks, two more questions:

-- What is an Hash Table ?

-- Is there a diference of usage between associatives and indexed arrays ?
I mean I can do

$array[0] = "12345";

if I access $array[0][1] I will have the number '2'.

I guess this can be done in the same using an associative array, perhaps something like

$array["name"] = "myname";

$array["name"][2] Will be 'n'. Is this correct ?

[ I don't have the PHP parser avaiable right now, so I can't test this. Thanks for your time.. ]

Answer to second question is yes. The examples you listed will all work.

Ok, thanks for your help.

Here's a better description of a hash table.