Unable to loop correct values from multidimensional array

Question

I am trying to learn about multidimensional arrays and have deliberately built the below array called $answerStringArray to practice on:

array(4) {
    [0] => array(1) {
        [0] => array(3) {
            [0] => string(8) "Swimming" 
            [1] => string(7) "Burgers" 
            [2] => string(3) "Bob"
        }
    }[1] => array(1) {
        [0] => array(3) {
            [0] => string(7) "Running" 
            [1] => string(5) "Chips" 
            [2] => string(4) "Paul"
        }
    }[2] => array(1) {
        [0] => array(3) {
            [0] => string(7) "Jogging" 
            [1] => string(5) "Salad" 
            [2] => string(5) "David"
        }
    }[3] => array(1) {
        [0] => array(3) {
            [0] => string(7) "Walking" 
            [1] => string(5) "Sauce" 
            [2] => string(5) "Frank"
        }
    }
}

I am trying to build a loop wherby I can echo the values

Swimming
Running
Jogging 
Walking

on the first iteration followed by

Burgers
Chips
Salad
Sauce

etc etc

I appreciate I could just write array[0][0][0]; to print Swimming etc etc, but I want to understand how to loop through to get the desired data.

I have tried using a loop as shown below, but it starts getting out of sync and then I realised that maybe that might be a bad way to be trying to do what I am after:

$arrayLength = count($answerStringArray);

 for($x = 0; $x <= $arrayLength; $x++){

        for ($y =0; $y<=$x; $y++) {

            for ($z =0; $z<=$y; $z++) {

            echo $answerStringArray[$x][$y][$z];

        }

      }
 }

"I appreciate I could just write array[0][0][0]; to print Swimming etc etc, but I want to understand how to loop through to get the desired data." -- That is the way to understand it. If you do it, you will see in which order you should loop over the indices, and if the loops really depend on the indices of outer loops. — tevemadar
– tevemadar, Commented Feb 19, 2018 at 23:55

tevemadar · Accepted Answer · 2018-02-20 10:49:13Z

I appreciate I could just write array[0][0][0]; to print Swimming etc etc, but I want to understand how to loop through to get the desired data.

That is exactly how you can understand. You just need to collect the array indices in the order you want to see the elements on screen:

Swimming -- [0][0][0]
Running  -- [1][0][0]
Jogging  -- [2][0][0]
Walking  -- [3][0][0]

Burgers  -- [0][0][1]
Chips    -- [1][0][1]
Salad    -- [2][0][1]
Sauce    -- [3][0][1]

Bob      -- [0][0][2]
Paul     -- [1][0][2]
David    -- [2][0][2]
Frank    -- [3][0][2]

Then you can look at the indices and see the patterns: for creating the groups, you have to loop over 0...3 at the first index:

for($x = 0; $x <= 3; $x++){
    echo $answerStringArray[$x][0][0] . "\n";
}                               // ^
echo "\n";
for($x = 0; $x <= 3; $x++){
    echo $answerStringArray[$x][0][1] . "\n";
}                               // ^
echo "\n";
for($x = 0; $x <= 3; $x++){
    echo $answerStringArray[$x][0][2] . "\n";
}                               // ^

Then you can make use of the marked index which seems to step from 0..2, one step per group. So wrap the whole thing into an outer loop:

for($z = 0; $z <= 2; $z++){
    for($x = 0; $x <= 3; $x++){
        echo $answerStringArray[$x][0][$z] . "\n";
    }
    echo "\n";
}

Then you can get rid of the hardcoded numbers, and make use of count() as you started in your code too:

$xcount = count($answerStringArray);
$zcount = count($answerStringArray[0][0]); // here we assume that all arrays look the same!

for($z = 0; $z < $zcount; $z++){ // "<= maxindex" became the more common "< size"
    for($x = 0; $x < $zcount; $x++){ // also here
        echo $answerStringArray[$x][0][$z] . "\n";
    }
    echo "\n";
}

And then we can add usage of the middle index, and get rid of extra linebreaks (the echo "\n"; line already produces an unneeded empty line at the end, and the soon introduced $y-loop would do the same between the blocks):

$answerStringArray=array(array(array("Swimming" ,"Burgers" ,"Bob"))
                        ,array(array("Running" ,"Chips" ,"Paul"))
                        ,array(array("Jogging" ,"Salad" ,"David"))
                        ,array(array("Walking" ,"Sauce" ,"Frank")));
//var_dump($answerStringArray);

echo "***\n";
$xcount = count($answerStringArray);
$ycount = count($answerStringArray[0]);
$zcount = count($answerStringArray[0][0]);    
for($z = 0; $z < $zcount; $z++){
    for($y = 0; $y < $ycount; $y++){
        for($x = 0; $x < $xcount; $x++){
            echo $answerStringArray[$x][$y][$z]."\n";
        }
        if($y < $ycount-1) echo "\n";
    }
    if($z < $zcount-1) echo "\n";
}
echo "***";

This works fine on sandbox.onlinephpfunctions.com

Thanks for for the detailed answer - I will now use this as a reference point going forward on best practice in regards to tackling this sort of scenario in future.

Sebastien D · Accepted Answer · 2018-02-20 00:35:03Z

0

Assuming all arrays are homogeneous, (they have the same length), you could do:

for($i = 0; $i<count($awnswerStringArray[0][0])){
    foreach($answerStringArray as $element){
       echo $element[0][$i];
    }
}

edited Feb 20, 2018 at 0:35

answered Feb 20, 2018 at 0:15

Sebastien D

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