UNSW ProgComp: Problem 5 - 2006

<?php

$input = <<<END
5
 1  9 12 20 23
17 25  3  6 14
 8 11 19 22  5
24  2 10 13 16
15 18 21  4  7
END;

function remove_empty($a){
    if($a){
        return true;
    }
}

$input = explode("\n", $input);
array_shift($input); //remove the first line
foreach($input as $key => $value){
    $input[$key] = explode(" ", $value);
}

foreach($input as $key => $value){
    $input[$key] = array_filter($input[$key], "remove_empty");
    $input[$key] = array_values($input[$key]);
}

//var_dump($input);
$numbers = array();

foreach($input as $key => $value){
    foreach($value as $number){
        if(in_array($number, $numbers)) die("Invalid data: missing or repeated number");
        $numbers[] = $number;
    }
}

sort($numbers);
//var_dump($numbers);

$last = 0;
for($x = 0; $x < count($numbers); $x++){
    if($numbers[$x] == $numbers[$x+1]) die("Invalid data: missing or repeated number");
}

//now actually test if each collum and row adds up
$sum = array();
$sum['diag1'] = 0;
$sum['diag2'] = 0;

for($x = 0; $x < count($input[0]); $x++){
    $sum['col'][$x] = 0;
    for($y = 0; $y < count($input); $y++){
        //$input[$y][$y] and we are moving down the collum
        $sum['col'][$x] += $input[$x][$y]; //add up in each collum, php should be alright with $sum[n] not having a preset value
    }
}

for($y = 0; $y < count($input); $y++){
    $sum['row'][$y] = 0;
    for($x = 0; $x < count($input[0]); $x++){
        $sum['row'][$y] += $input[$x][$y];
    }
}

for($z = 0; $z < count($input); $z++){
    $sum['diag1'] += $input[$z][$z];
    $sum['diag2'] += $input[$z][count($input)-$z-1];
}

//var_dump($sum);

if($sum['diag1'] != $sum['diag2']) die("Invalid data: inconsistent sums");
$last = $sum['diag1'];
for($x = 0; $x < count($input); $x++){
    if($last != $sum['col'][$x]) die("Invalid data: inconsisten sums");
    if($last != $sum['row'][$x]) die("Invalid data: inconsisten sums");
}

echo "Magic square";