Names for PHP query results and PHP loops. - php

Question

This might be a simple question, but I can't find a definitive answer I can understand. I use PHP loops alot, I'm fairly new to PHP so they are usually simple like so:
<?php
$result = mssql_query("SELECT Price FROM Window_Extras WHERE ExtraID = '4' ");
while ($row = mssql_fetch_array($result)) {
?>
<a title="<?php echo $row['Colour']; ?>"></a>
<?php }?>
Is a really simple example, that doesn't make much sense, but I hope it shows how I use them. The question I wanted to ask was if $row and $result have to be named that for it to work, could they for example be named $priceresult and $pricerow?
This is because sometimes I would like to use multiple queries for a single loop, for example:
<?php
$result = mssql_query("SELECT Price FROM Extras WHERE ExtraID = '4' ");
$colourresult = mssql_query("SELECT ColourID FROM Colours WHERE Type = '8' ");
while ($row = mssql_fetch_array($result, $colourresult)) {
?>
This however didn't work, when I tried to echo out:
<?php echo $row['ColourID']; ?>
Can anyone tell me how I should be approaching this, and if I am at all on the correct track. Sorry if I havn't explained it very well.

Answer 1

To answer your first question:
Yes, you can use any variable name you like for the result and row variables. PHP doesn't care what you call them, and in fact it's perfectly possible to have several of them in use at any given time, in which case they obviously need to have different names.
You then followed up that question by asking why the following code doesn't work:
$result = mssql_query("SELECT Price FROM Extras WHERE ExtraID = '4' ");
$colourresult = mssql_query("SELECT ColourID FROM Colours WHERE Type = '8' ");
while ($row = mssql_fetch_array($result, $colourresult)) {
....
}
The reason for this is that the _fetch_array() function can only work with one set of results at a time. You would need to fetch a separate row array for each of them.
It's not clear what you're trying to do with these two queries, and why you would want to put them into the same loop together in the way you've shown.
I'm going to assume that the two queries are linked in some way that makes it logical for you to use them together like this? Perhaps the Extra item you're loading has a known Colour; ie you know that the Extra item numbered 4 is coloured with the Colour numbered 8?
Typically a program wouldn't be written with this knowledge; it would be part of the data. So in the Extras table, you would have a ColourID field, which would contain the value 8. The program would load the Extras record, see that the ColourID was set, and then load the matching Colours record according to what it saw.
Thus, your code could look something like this:
$result = mssql_query("SELECT Price FROM Extras WHERE ExtraID = '4' ");
while ($row = mssql_fetch_array($result)) {
$colourresult = mssql_query("SELECT ColourID FROM Colours WHERE Type = '".$row['colourID']."' ");
while ($row2 = mssql_fetch_array($result)) {
....
}
}
Inside the inner while loop, you could then access fields from either query, using $row or $row2 respectively (again, you can name these as you see fit).
However, that's not the end of the story, because SQL actually has the ability to merge these two queries into one without needing all that PHP code, using a thing call a SQL JOIN.
Now we can write a more complex query, but go back to having simpler PHP code:
$result = mssql_query("SELECT Extras.Price, Colours.ColourName FROM Extras WHERE ExtraID = '4' INNER JOIN Colours ON Colours.ColourID = Extras.ColourID");
while ($row = mssql_fetch_array($result)) {
....
}
If you're a beginner in PHP and SQL, these concepts are all probably new to you, so I advise trying them out, experimenting with them, and most importantly, reading a few (good quality) tutorials about them before proceeding much further.
Hope that helps. :)
(PS: as I said above, make sure you're reading good tutorials; beware of bad PHP examples and teaching sites -- there's a lot of them out there, teaching poor code and obsolete techniques; make sure you're reading something worthwhile. A good place to start might be http://phpmaster.com/)

Answer 2

This is because mssql_fetch_array can only take one result set. So removing $result and leaving $colourresult should work for you.
See: http://php.net/manual/en/function.mssql-fetch-array.php

Answer 3

Your variables ($...) can be called whatever you want, it's generally better to name them in a way that you can understand, hence most of the examples in the PHP Manual contain variables like $row, $result, $query, etc.
In terms of your database query, you can only pass one query to the mssql_query method. If you have data from different tables that you need to display, you should try and join the tables if possible using SQL rather than looping through multiple result sets.