保持多维数组的语义？

Today's the first day I've really gotten stuck into creating anything from scratch in PHP7. My script skills are pretty rudimentary anyway, so I apologise in advance.

I've been looking at tutorial pages + searching Google/Stack and can't seem to find the answer to a few basic syntax questions about Multidimensional Arrays (MDAs).

The tutorials I've read show MDAs as follows:

MDA Tutorial Example:

http://webcheatsheet.com/php/multidimensional_arrays.php https://www.w3schools.com/php/php_arrays_multi.asp

$a = array(array(array("a", a2, a3),
                 array("b", b2, b3),
                 array("c", c2, c3) 
                 ),
           array(array("a", a2, a3),
                 array("b", b2, b3),
                 array("c", c2, c3) 
                 ),
           array(array("a", a2, a3),
                 array("b", b2, b3),
                 array("c", c2, c3) 
                 )
           );

As all the layers are simply named array and W3 only calls the parent variable with numerical values for [$row] [$col] it's unclear what solutions there are for naming and labeling elements in the array with custom handles.

Example 6 on PHP.net shows something that looks along the right lines, but it's not an exact demonstration.

Using the array shorthand which I'm more familiar with, would something like this work?

For Example:

    $a = [Custom1[Custom2[Custom3["a", a2, a3],
                         Custom3["b", b2, b3],
                         Custom3["c", c2, c3] 
                         ],
    //**does each level require the same naming as the level above
                 Custom2[Custom3["a", a2, a3],
                         Custom3["b", b2, b3],
                         Custom3["c", c2, c3] 
                         ],
    //**Or Are they independent and customised freely            
                    Fred[Wez["a", a2, a3],
                         Otto["b", b2, b3],
                         Sam["c", c2, c3] 
                         ]],
                   ];

I'm sure this is a fairly basic question, but as I said, I just couldn't seem to find an answer.

I think the concept you are looking for is simply "associative arrays".

You could create something like this (trying to use your example).

$a = [
    'Custom1' => [
        'Fred' => [
            'Wez' => ["a", a2, a3],
            'Otto' => ["b", b2, b3],
            'Sam' => ["c", c2, c3]
        ]
    ]
];

To access to an element here you have to do it this way:

$element = $a['Custom1']['Fred']['Otto'][2]; // Last array is numeric
// Now $element has b3.

Remember you can't use the same index more than one time into each array. So you couldn't do this:

$a = [
    'Custom1' => [
        'Custom2' => [],
        'Custom2' => []
    ]
];

Here you can read more about php arrays.

Also, as said in comments, array() is just a function you use to create the array, but your are not naming it in any way. Since PHP 5.4, you can use [] notation, which I in my opinion, keeps the code cleaner.