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I'm developing a room booking system using PHP for a school project.

I'm trying to create a variable name by concatenating values from two arrays together. here are the two arrays:

$day = array('Mon', 'Tue', 'Wed', 'Thu', 'Fri');
$B = array('P1B', 'P2B', 'P3B', 'P4B', 'P5B', 'P6B');

and then here is the code I'm currently using to try concatenate them:

// getting all the values from the table using $_POST. There are 120 different values so it is best to create these variables using a procedure

for ($l = 0; $l < count($day); ++$l) {
    for ($k = 0; $k < count($B); ++$k) {
        $days = $day[$l];
        $week = $B[$k];
        ${$days . $week} = $_POST["'" . $days.$week . "'"];
    };
};

Is the syntax of the concatenated variable correct? Is there a better way of doing this?

The final variable names of the concatenated variable should look something like:

$MonP1B
$MonP2B
$MonP3B
$MonP4B
$MonP5B
$MonP6B
$TueP1B

etc.

share|improve this question
3  
This is a really bad idea, storing each value as a variable will make it really difficult to use. You are far better off storing them in array like it already is in the $_POST array, or better yet a multi-dimensional array so you can reference a day at a time. –  bumperbox Nov 17 '14 at 19:31
    
Also consider using an off-the-shelf software package instead of writing your own. –  200_success♦ Nov 17 '14 at 20:26
    
@bumperbox Sounds like a better idea than the original (storing in a multi-d array). Off-the-shelf is something I cannot use as the project is one for coursework and requires me to code a system myself :) thank you Bumperbox! –  Yash Morar Nov 17 '14 at 21:54

1 Answer 1

up vote 2 down vote accepted

I have to agree with bumperbox here - why create separate variables instead of using an array to store them all, as follows:

$day = array('Mon', 'Tue', 'Wed', 'Thu', 'Fri');
$B = array('P1B', 'P2B', 'P3B', 'P4B', 'P5B', 'P6B');
$arr = array();

for ($l = 0; $l < count($day); ++$l) {
    for ($k = 0; $k < count($B); ++$k) {
        $days = $day[$l];
        $week = $B[$k];
        $arr[$days . $week] = $_POST["'" . $days.$week . "'"];
    }; 
};

Which would generate:

Array
(
    [MonP1B] => 
    [MonP2B] => 
    [MonP3B] => 
    ...
    [FriP4B] => 
    [FriP5B] => 
    [FriP6B] => 
)

And which you can access via $arr['FriP5B'] for example.

Now, as to how you can improve your code, see this:

$days_of_the_week = array('Mon', 'Tue', 'Wed', 'Thu', 'Fri');
$number_of_days = count($days_of_the_week);
$rooms = array('P1B', 'P2B', 'P3B', 'P4B', 'P5B', 'P6B');
$number_of_rooms = count($rooms);
$booked_day_room = array();

for ($day = 0; $day < $number_of_days; ++$day) {
    for ($room = 0; $room < $number_of_rooms; ++$room) {
        $days_room = $days_of_the_week[$day] . $rooms[$room];
        $booked_day_room[$days_room] = isset($_POST[$days_room]) ?: $_POST[$days_room];
    };
};

print_r($booked_day_room);

What we did:

  1. Used descriptive variable names
  2. Cached the count() function calls
  3. Stored everything in 1 array, so we don't have to chase 100 different variables

Why are we using an array over multiple variables? Multiple variables might be a bit faster, and they might use more or less the same memory, however from a code readability standpoint, you want one array as it is easier to keep track of in the code.

share|improve this answer
    
You might want to add isset around $_POST in-case there are non-existent keys –  bumperbox Nov 17 '14 at 20:10
    
Good call, adding it in –  jsanc623 Nov 17 '14 at 21:16

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