Multi-Dimensional Arrays Help - And Other Questions on Arrays

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For some reason, I have always had a hard time understanding arrays as they pertain to php and databases. I understand associative arrays just fine but when there are multidimensional arrays, I kinda don't.

I have gone over a few different examples but they were limited. I was able to find one piece of code that I would like to disect and ask questions about so I can gain a better understanding.

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 $characters = array

(

  array ( name=>"name 1"

  , occupation=>"developer"

  , age=>30

  , specialty=>"Java"

  ),

  array

  (

    name=>"name 2"

    , occupation=>"Programmer"

    , age=>24

    , specialty=>"C++"

  ),

  array

  (

  name=>"name 3"

  , occupation=>"designer"

  , age=>63

  , specialty=>"Javascript"

  )

);
 
foreach ($characters as $val)

{

  foreach ($val as $key=>$final_val)

  {

    print "$key: $final_val<br>";

  }

  print "<br>";

}

In this code, the way I am reading this is that there are 3 "rows"??? or blocks of data. Each one of these rows or blocks has several other rows inside of it. I don't have a problem with the arrays per se but more the foreach loop. If I am incorrect about these 3 arrays being rows, please feel free to correct me.

On the foreach, can someone please tell me exactly how and why it is set up the way it is? Specifically, I don't understand why the coder didn't use a key/value pair. He only uses a value, then inside the loop he uses $key=>$final_val. What I need to understand is why and when to refer to or use the key value pair and when not to. I have also seen code written inside the foreach loop like so: $key['something'] = $val;

What is that? What exactly does it do? If any one can help me to understand these, I would be forever grateful. I have pulled my hair out for the last time on drawing my data out of an array.

Thanks.

Apr 21 '09 #1

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110

6849

Dormilich

8,658

Expert Mod 8TB

firstly, the posted code should give you quite a bunch of error notices (the keys are set as constants, which I doubt are intended)

if you're familiar with Maths, imagine arrays as matrices where you can access each element with the appropriate index (aka key) values (like $array[$i][$j][$k]). the sample would correspond to a 3x4 matrix.

@fjm
the reason for not using a key/value pair in the first loop is, that the keys are not needed by the program/coder (they are numeric values). in the first foreach he loops through the topmost array getting an array as value ($val) (gettype($val) would give you "array") then he loops over that value/this array and prints the keys ($key) and values ($final_val) of this sub-array.

foreach can be used in 2 ways, so you can use the syntax you really need:

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 // values only

foreach ($array as $value)
 
//keys and values

foreach ($array as $key => $value)

@fjm
it depends on what you want to do, if you don't need the keys you omit them.

@fjm
looks strange, I need to see the whole code (part) to explain.

Apr 21 '09 #2

Ciary

247

Expert 100+

@Dormilich
shouldn't that be something like this?

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$array[$key]=$val;

or for an associative array:

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$array['something']=$val

in this case, it's used to write to the array in a foreach loop to change its values. next is a multidimentional example based on your array.

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$i = 0;

foreach($array as $key => $val){

   $val[0] = "changedname " + $i;

   $i ++;

   $array[$key] = $val;

}

this code changes the first value on each row to "changedname " and the row number. to do this you need a key but mostly you wont use it. mostly, you need it when you want to write to the array.

the code as you wrote it cant be right. it states that your $key is an array. or it could be a foreign library i dont know about.

Apr 21 '09 #3

Multi-Dimensional Arrays Help - And Other Questions on Arrays

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