$weapons = explode("-",$row['weapons']);
$len = sizeof($weapons);
$weapons2 = "";
for ($i=0;$i<$len;$i++) {
    if ($i == 2) { //третий ноль
      $weapons2 .= "1-";
    } else {
      $weapons2 .= $weapons[$i]."-";
    }
}
$result = substr($weapons2, 0, -1);

$weapons = explode("-",$row['weapons']);
$len = sizeof($weapons);
for ($i=0;$i<$len;$i++) {
   if ($i == 2) { //третий ноль
      $weapons2[] = "1";
    } else {
      $weapons2[] = $weapons[$i];
    }
}
result = implode("-",$weapons2);

0-0-1-0-0-0-0-0-0-0-0

<?php
$production = explode("-","15-6-6-6-0");
?>

<?php
$production = explode("-","15-6-6-6-0");
$production[4] = 10;
$result = implode("-",$production);
?>