Question

I am trying this loop, but i have a problem in $m[2][3]. None value is showed. So i have some problem with increments.

$nArr = array('A', 'B', 'C', 'D', 'E', 'F');

$lp = 4;

for ($i = 0; $i < $lp; $i++) {
    $m[$i][$i] = 1;
    for ($x = $i; $x < $lp; $x++) {
        $v = $i+$i;
        $m[$i][$x+1] = $nArr[$x+$v];
    }
}

this is my output :

1 + A + B + C + - 1 + D + E + - 1 +   + - 1 +

The output that i want:

1 + A + B + C + - 1 + D + E + - 1 + F + - 1 +

in detail:

echo $m[0][0]."+"; 1
echo $m[0][1]."+"; A
echo $m[0][2]."+"; B
echo $m[0][3]."+"; C
echo " - ";
echo $m[1][1]."+"; 1
echo $m[1][2]."+"; D
echo $m[1][3]."+"; E
echo "- ";
echo $m[2][2]."+";1
echo $m[2][3]."+"; //error, must be F
echo "- ";
echo $m[3][3]."+"; 1

Answer 1

Your problem is in your progression. In the second “for” your progression increases rapidly:

$v = $i+$i;         
$m[$i][$x+1] = $nArr[$x+$v]; 

• In the first iteration starts with 0 + 0 + 0 ($ x + $ i + $ i) = 0 =
  “A”
• In the second iteration begins with 1 + 1 + 1 ($ x + $ i + $ i) = 3 =
  “D”
• and the third iteration begins with 2 + 2 + 2 ($ x + $ i + $ i) = 6 =
  null, your array has 6 elements so your max index is 5.

You should change the progression in order to get the next progression of indexes: 0, 3, 5.

Try this:

$nArr = array('A', 'B', 'C', 'D', 'E', 'F');
$lp = 4;                
for ($i = 0; $i < $lp; $i++) {
     $m[$i][$i] = 1;            
    for ($x = $i; $x < $lp; $x++) {                
        $v = $i+ceil($i/2);
        $m[$i][$x+1] = $nArr[$x+$v];            
    }        
}