How to populate PHP 3D array from MySQL

Question

As my previous questions simplify I am trying to learn 3D arrays in PHP but each lesson is getting difficult to understand by me.

I have prepared code with empty 3D (layered) array but don't know how to:

populate it with data from MySQL database
display it/reffer to it like: echo $result_value[x][y][z] gives value

.

include_once 'connect.php';

$player_id = '6';
$result_value = array();

$pullMapInfo = "SELECT x, y, z, value FROM mapinfo WHERE id='{$player_id}'";
$pullMapInfo2 = mysql_query($pullMapInfo) or die(mysql_error());

while ( $pullMapInfo3 = mysql_fetch_assoc($pullMapInfo2) ) {
    $result_value = array(
                          array(
                              array('', '', ''),
                              array('', '', ''),
                              array('', '', ''),
                          ),
                          array(
                              array('', '', ''),
                              array('', '', ''),
                              array('', '', ''),
                          ),
                          array(
                              array('', '', ''),
                              array('', '', ''),
                              array('', '', ''),
                          )
                      );
}

for($z = 1; $z <= 3; $z++){
for($x = 1; $x <= 16; $x++){
for($y = 1; $y <= 16; $y++){
    # echo database row's divided among layers (z parameter) for ex.: 1,1,1 = red (X,Y,Z = color value) - 1 width & 1 height on 1st layer contains red value
    # to get access to it like this: $result_value[x][y][z] => [value];
}
}
}

It's often more convenient to have a clear view of the context of a question, and sometimes it allows us to give a better answer with an alternative approach to the problem. In that case I could have suggested a OOP alternative with a 3dPoint class and mysql_fetch_object for example. It is also considered nice to answer people willing to help you when they request clarification. — Tchoupi
– Tchoupi, Commented Sep 13, 2012 at 12:02

LSerni · Accepted Answer · 2012-09-13 12:31:18Z

1

populate it with data from MySQL database
display it/reffer to it like: echo $result_value[x][y][z] gives value

The population stage is simply selecting at least x, y, z and value fields.

Then, in a loop, you retrieve all the data. At that point you check whether the array prerequisites are present, if they aren't you set them up, and set the value:

<?php
    $db = mysql_connect($db_host,$db_user,$db_password) or die($error[0])

    $arr3d = array();

    /* Initialization to get a "dense" array
    $z_row = array_fill(0, $max_z, '<DEFAULT>');
    $y_row = array_fill(0, $max_y, $z_row);
    $arr3d = array_fill(0, $max_x, $y_row);
    unset($y_row, $z_row); // Do not waste memory
    */

    $query = 'SELECT x, y, z, value FROM ...;'   ;

    $handle = mysql_query($query) or die("$query: error: " . mysql_error());

    while($row = mysql_fetch_array($handle))
    {
        // $row is an array with x, y, z and value keys in this order
        list($x, $y, $z, $value) = $row;

        /* This if we had used mysql_fetch_assoc instead
        $x = $row['x'];
        $y = $row['y'];
        $z = $row['z'];
        $value = $row['value'];
        */
        if (!isset($arr3d[$x]))
            $arr3d[$x] = array();
        if (!isset($arr3d[$x][$y]))
            $arr3d[$x][$y] = array();
        $arr3d[$x][$y][$z] = $value;
    }
    mysql_free_result($handle);
?>

In case you want a full ("dense") array, you have to first loop x, y and z through all their values and assign a default value to array cells, to be overwritten by the SQL loop.

In the code above, with dense patch left commented, if there is no row with x=5, y=2 and z=3, $arr3d[5][2][3] will be undefined.

edited Sep 13, 2012 at 12:31

answered Sep 13, 2012 at 11:41

LSerni

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8 Comments

Szymon Toda Over a year ago

How to test your code with $db = mysql_connect($db_host,$db_user,$db_password) or die($error[0]);? Also I get Undefined function SQLFetchRow

LSerni Over a year ago

I have updated my answer; you'll need to supply DB connection parameters and exact query syntax for it to be acceptable.

Szymon Toda Over a year ago

Fatal error: Call to undefined function mysql_free() in pastebin.com/s9dPiJRX on line 44

LSerni Over a year ago

Ah, sorry. it was mysql_free_result().

Szymon Toda Over a year ago

How to alter it to echo values (inside while-loop) only if they are actually in DB?

|

mtsvetkov · Accepted Answer · 2012-09-13 12:00:55Z

0

mysql_fetch_assoc($pullMapInfo2) will return an array that you can use to get the X,Y, and Z values of your player like so:

$x = $pullMapInfo3["x"]
$y = $pullMapInfo3["y"]
$z = $pullMapInfo3["z"]

If you want to put that in your result_value array you can the simply $result_value[$x][$y][$z] = $pullMapInfo3["value"].

Also, move the initialization of $result_value out of the loop to where you wrote $result_value = array();:

for ($ix = 1; $ix <= 16; $ix++) {
    $result_value[$ix] = array();
    for ($iy = 1; $iy <= 16; $iy++) {
        $result_value[$ix][$iy] = array();
    }
}

Then you can use the loop from the pastebin. Also note that you're just going to get Layer 1, Layer 2, Layer 3 at the output + 768 <br> tags, so I'm not sure if that's what you meant to do.

edited Sep 13, 2012 at 12:00

answered Sep 13, 2012 at 11:38

mtsvetkov

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4 Comments

Szymon Toda Over a year ago

This lags a little and outputs Layer 1: pastebin.com/sJJsJrfF

mtsvetkov Over a year ago

It did that because you don't instantiate the subarrays. You just set $result_value to array(), which means it's 1 dimensional. First thing in the iz loop: $result_value[$iz]=array(), then in the ix loop: $result_value[$iz][$ix] = array(). Note that this will mean its addressing will be ...[z][x][y]. If you want it to be [x][y][z], you'll have to write a separate loop to build up the arrays before using them. It's only outputting layer 1 because it fails to do the first $result_value[$x][$y][$z] lookup after entering the loop.

mtsvetkov Over a year ago

New code in the edit shows how to set up $result_value. Put that right after $result_value = array()

mtsvetkov Over a year ago

This (pastebin) displays Layer 1, Layer 2, and Layer 3. I've used dummy values. Check to see that the x,y, and z you're getting from the database are in the proper ranges.

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