undefined offset in BoxArray - php

Question

I'm trying to calculate the volume of each box but I keep coming across errors and I don't know how to fix it. Everything seem correct and I followed how the book's example.
This is the error it gave me in this code:
"Notice: Undefined offset: 0 in C:\wamp\www\BoxArray.php on line 16"
<?php
$BoxMeasurements = array("sBox" => array("length" => 12, "width" => 10, "depth" => 2.5),
"mBox" => array("length" => 30, "width" => 20, "depth" => 4),
"lBox" => array("length" => 60, "width" => 40, "depth" => 11.5));
$BoxMeasurements = array_slice($BoxMeasurements, 0, 3);
echo "The box sizes are:";
for($i = 0; $i < count($BoxMeasurements); ++$i)
{
echo "$BoxMeasurements[$i]";
}
?>
When I tried doing it the other way I got this error:
"Parse error: syntax error, unexpected '=', expecting ')' in C:\wamp\www\BoxArray.php on line 8"
<?php
$sBox = array("length" => 12, "width" => 10, "depth" = 2.5);
$mBox = array("length" => 30, "width" => 20, "depth" = 4);
$lBox = array("length" => 60, "width" => 40, "depth" => 11.5);
$dimension = array($sBox, $mBox, $lBox);
echo "$dimension[0][0]";
?>
Is there a special way to call the variable/array name?

Answer 1

$BoxMeasurements is declared as an associative array, which means you should access its values with the keys you defined in the declaration: "sBox", "mBox" and "lBox".
In order to iterate over this kind of arrays you can use the foreach form:
<?php
$BoxMeasurements = array("sBox" => array("length" => 12, "width" => 10, "depth" => 2.5),
"mBox" => array("length" => 30, "width" => 20, "depth" => 4),
"lBox" => array("length" => 60, "width" => 40, "depth" => 11.5));
echo "<pre>";
echo "The box sizes are:\n";
foreach($BoxMeasurements as $name => $size)
{
$volume = $size['length'] * $size['width'] * $size['depth'];
echo " - $name: $volume\n";
}
echo "</pre>";
?>
OUTPUT
The box sizes are:
- sBox: 300
- mBox: 2400
- lBox: 27600

Answer 2

You seem not to understand difference between variable name and variable content, as indicated by using " around names. It's pointless. It should be
echo $BoxMeasurements[$i];
While assigning your array, correct syntax is:
key => value
while some of your "rows" are assigned just "key = value" which throws syntax error.
Also you try to access array by numerical indices, while your array does not use them. Use foreach to iterate the array:
foreach( $BoxMeasurements as $key=>$val ) {
echo $val;
}
Finally, you should be doing post increment in your for loop, not pre increment.
I strongly suggest to spend some time and go through some tutorials as you made too many elementary errors.