Array basics

[Tom_Tees]

Need some help with understanding how arrays work.

(I'm reading a book on e-commerce, and the author has a really peculiar way of coding?!)

So, there is a stored procedure

Catalog::GetDepartments();

Its output should be this...

department_id	name
--------------	---------
0		Regional
1		Nature
2		Seasonal

The author just assigned a class variable to the stored procedure like this...

$this->mDepartments = Catalog::GetDepartments();

How do the query results get stored into the "mDepartments" variable?

TomTees

[bradgrafelman]

Tom Tees wrote:

How do the query results get stored into the "mDepartments" variable?

The return value of the GetDepartments() static method is stored in that class property.

If you're expecting a more specific response, then you'll have to show us the code for the GetDepartments() method.

[Tom_Tees]

bradgrafelman;10953982 wrote:

The return value of the GetDepartments() static method is stored in that class property.

If you're expecting a more specific response, then you'll have to show us the code for the GetDepartments() method.

I don't understand?

I provided the SQL output...

department_id	name
--------------	---------
0		Regional
1		Nature
2		Seasonal

and didn't include the query since it didn't relevant. (It's just a simple SELECT query.)

SELECT department_id, name
FROM department
ORDER BY department_id;

TomTees

[bradgrafelman]

You haven't shown us anything about Catalog::GetDepartments(), so how are we supposed to know what that static method is doing?

[Tom_Tees]

bradgrafelman;10953988 wrote:

You haven't shown us anything about Catalog::GetDepartments(), so how are we supposed to know what that static method is doing?

CREATE PROCEDURE catalog_get_departments_list()
BEGIN
	SELECT department_id, name
	FROM department
	ORDER BY department_id;
END$$

public static function GetAll($sqlQuery, $params = null, $fetchStyle = PDO::FETCH_ASSOC)
...

class Catalog {
	public static function GetDepartments(){
		$sql = 'CALL catalog_get_departments_list();

return DatabaseHandler::GetAll($sql);
}
}

Is that what you are asking for?

TomTees

[bradgrafelman]

Yes, that shows us what GetDepartments() is returning.

Now, what's your question? How does $this->mDepartments become an array of the rows retrieved from your DB?

[Tom_Tees]

bradgrafelman;10953996 wrote:

Yes, that shows us what GetDepartments() is returning.

Now, what's your question? How does $this->mDepartments become an array of the rows retrieved from your DB?

I understand that PHP is dynamically creating an array for me.

My question was "How do the query results get stored into the "mDepartments" variable?"

In other words, what is the array structure that PHP decided to use?

(I'm trying to understand this author's coding style, and not having a way to write the code right now, I could use some help understanding what the array that PHP created looks like.

Based on that answer, I have a related question I need help figuring out.)

TomTees

[bradgrafelman]

Well to answer that question, you'd have to look at what DatabaseHandler::GetAll() is returning.

Some DB drivers have functions that will loop through the result set and build the array for you, such as mysql_result::fetch_all() (see manual page: [man]mysqli-result.fetch-all[/man]).

[Tom_Tees]

It could like this...

mDepartments = array(
array('', 'department_id', 'name'),
array(0, 0, 'Regional'),
array(1, 1, 'Nature'),
array(2, 2, 'Seasonal'))

Or maybe like this...

mDepartments = array(
array('department_id', 'name'),
array(0, 'Regional'),
array(1, 'Nature'),
array(2, 'Seasonal'))

TomTees

[Tom_Tees]

bradgrafelman;10954000 wrote:

Well to answer that question, you'd have to look at what DatabaseHandler::GetAll() is returning.

Some DB drivers have functions that will loop through the result set and build the array for you, such as mysql_result::fetch_all() (see manual page: [man]mysqli-result.fetch-all[/man]).

Okay, but I also posted this snippet...

public static function GetAll($sqlQuery, $params = null, $fetchStyle = PDO::FETCH_ASSOC)

Isn't that enough to help you help me figure things out?

TomTees

[bradgrafelman]

Tom Tees wrote:

Okay, but I also posted this snippet

Ah, I hadn't seen that earlier - I had already begun composing my reply, apparently, by the time you added that to your post.

Tom Tees wrote:

Isn't that enough to help you help me figure things out?

If I showed you:

protected function GoBananas($go, $gogo, $bananas = true)

could you explain to me what that function does or what it might return? 😉

The snippet you posted does, however, reveal one important piece of information - that you're using the PDO interface. The PDO interface also provides a method for fetching all rows in a result set into an array: [man]pdostatement.fetchall[/man].

[Tom_Tees]

bradgrafelman;10954004 wrote:

Ah, I hadn't seen that earlier - I had already begun composing my reply, apparently, by the time you added that to your post.

If I showed you:

protected function GoBananas($go, $gogo, $bananas = true)

could you explain to me what that function does or what it might return? 😉

The snippet you posted does, however, reveal one important piece of information - that you're using the PDO interface. The PDO interface also provides a method for fetching all rows in a result set into an array: [man]pdostatement.fetchall[/man].

I read that link and it didn't really help.

(I'm starting to think I should use this book as a doorstop and stop wasting time trying to learn someone else's code?!)

To further complicate things, here was my original question...

Below is some code from a not-so-well-written book on PHP that I'm reading...

for ($i=0; $i<count($this->mDepartments); $i++)
	$this->mDepartments[$i]['link_to_departments']
		= 'index.php?DepartmentId=' . $this->mDepartments[$i]['department_id'];

I believe this is all PHP code (and not Smarty code).

These are the parts I don't get in particular...

$this->mDepartments[$i]['link_to_departments']

$this->mDepartments[$i]['department_id'];

It looks like he is dynamically adding another "column" to the array, because "link_to_department" was not originally in the SQL/table I originally posted above.

My logic was, "If I can figure out what the array that PHP created for me, then maybe I can figure out what he added and is doing?!"

I don't like that he just uses "mDepartments" without more clearly defining what it is..

TomTees

[bradgrafelman]

Tom Tees wrote:

It looks like he is dynamically adding another "column" to the array, because "link_to_department" was not originally in the SQL/table I originally posted above.

That sounds like the gist of it, yeah.

$this->mDepartments is just a multidimensional array where each item is an array that represents a row retrieved from the DB. Thus $this->mDepartments[$i] refers to a the ith row retrieved, and $this->mDepartments[$i]['link_to_departments'] is a new pseudo-column in that row.

[Tom_Tees]

bradgrafelman;10954008 wrote:

That sounds like the gist of it, yeah.

$this->mDepartments is just a multidimensional array where each item is an array that represents a row retrieved from the DB. Thus $this->mDepartments[$i] refers to a the ith row retrieved, and $this->mDepartments[$i]['link_to_departments'] is a new pseudo-column in that row.

Okay, but that ties back to my original post.

The table was originally like this...

department_id	name
--------------	---------
0		Regional
1		Nature
2		Seasonal

So, when he assigns that data to "mDepartments", what does the array structure look like?

Is there an additional "column" (e.g. ID) that also reads: 0, 1, 2?

Does $this->mDepartments[$i] refer to the "department_id" or some new "ID" field that PHP added?

And, was ['link_to_departments'] then added on the tail-end like a new "column"?!

After he was done surreptitiously adding that, did the array maybe look like this...

It could like this...

mDepartments = array(
array('', 'department_id', 'name', 'link_to_departments'),
array(0, 0, 'Regional', ''),
array(1, 1, 'Nature', ''),
array(2, 2, 'Seasonal', ''))

or like this...

mDepartments = array(
array('department_id', 'name', 'link_to_departments'),
array(0, 'Regional', ''),
array(1, 'Nature', ''),
array(2, 'Seasonal', ''))

TomTees

[bradgrafelman]

Sounds like you either need to find some basic tutorials that talk about what an array is (or, more specifically, a multi-dimensional array... e.g. an array of arrays) and/or use [man]print_r/man to see what the array structure looks like.

[NogDog]

To discover how the result array is organized, you could simply add a bit of debug code for now:

$this->mDepartments = Catalog::GetDepartments();
echo "<pre>DEBUG:\n" . print_r($this->mDepartments, true) . "</pre>";

My guess is that it will be something like:

array {
    [0] => array {
        'department_id' => 0
        'name' => 'regional'
    }
    [1] => array {
        'department_id' => 1
        'name' => 'nature'
    }
}