PHP: Why does this return “undefined offset” every time?

So basically this is an algorithm I made for a battleships game. I’m having problems with the while loop, I want to have the code inside the do while loop keep repeating, if the generated values already exist in a multidimensional array, and it looks like it actually works, because it generates correct values, but I keep getting the error “UNDEFINED OFFSET”, why? And yes, I know it’s ugly code, but I’m really just interested in the error, because the program works fine otherwise

 $_SESSION["ladjica1"] = array("", "", "", "", "");
$_SESSION["ladjica2"] = array("", "", "", "");
$_SESSION["ladjica3"] = array("", "", "");
$_SESSION["ladjica4"] = array("", "", "");
$_SESSION["ladjica5"] = array("", "");
$_SESSION["ladjica"] = array(
    $_SESSION["ladjica1"],
    $_SESSION["ladjica2"],
    $_SESSION["ladjica3"],
    $_SESSION["ladjica4"],
    $_SESSION["ladjica5"]
    
);


function multi_array_iskanje($search_for, $search_in) {
    foreach ($search_in as $element) {
        if ( ($element === $search_for) || (is_array($element) && multi_array_iskanje($search_for, $element)) ){
            return true;
        }
    }
    return false;
}





function generirajLadjo($dolzina, $sirina, $indeksladje) {
do {
$ladjicaROW = rand(1,10)*10-1;
$ladjicaCOL = rand(1,10);
$zacetniPolozaj = $ladjicaROW + $ladjicaCOL;
    
    

for($sir = 0; $sir < $sirina; $sir++) {
$HaliV = rand(0,1);
if($HaliV == 1) {
    if($ladjicaCOL > $dolzina) {
        for($x = 0; $x < $dolzina; $x++) {
            $_SESSION["ladjica".strval($indeksladje)][$x] = $zacetniPolozaj - $x;
        }
    } else {
        for($x = 0; $x < $dolzina; $x++) {
            $_SESSION["ladjica".strval($indeksladje)][$x] = $zacetniPolozaj + $x;
        }
    }
    
} else {
    if(($ladjicaROW > ($dolzina*10)) && $ladjicaROW % 10 != 0) {
        for($x = 0; $x < $dolzina; $x++) {
            $_SESSION["ladjica".strval($indeksladje)][$x] = $zacetniPolozaj - ($x*10);
        }
    } else {
        for($x = 0; $x < 5; $x++) {
            $_SESSION["ladjica".strval($indeksladje)][$x] = $zacetniPolozaj + ($x*10);
        }
        
    }
    
}
}
 } while(multi_array_iskanje($_SESSION["ladjica".strval($indeksladje)][$x], $_SESSION["ladjica"])==true);

  }  
generirajLadjo(5, 1, 1);
generirajLadjo(4, 1, 2);
generirajLadjo(3, 1, 3);
generirajLadjo(3, 1, 4);
generirajLadjo(2, 1, 5);

Answer

Because a for loop will increment the counter and then test it your do-while limiting statement was using $x = 5 and that blew

$_SESSION["ladjica".strval($indeksladje)][$x]

beyond its bounds.

All I did was $x--; as the last thing before completing the loop and bingo. No erors.

$_SESSION["ladjica1"] = array("", "", "", "", "");
$_SESSION["ladjica2"] = array("", "", "", "");
$_SESSION["ladjica3"] = array("", "", "");
$_SESSION["ladjica4"] = array("", "", "");
$_SESSION["ladjica5"] = array("", "");
$_SESSION["ladjica"] = array(
                        $_SESSION["ladjica1"],
                        $_SESSION["ladjica2"],
                        $_SESSION["ladjica3"],
                        $_SESSION["ladjica4"],
                        $_SESSION["ladjica5"]
                    );


function multi_array_iskanje($search_for, $search_in) 
{
    foreach ($search_in as $element) {
        if ( ($element === $search_for) || (is_array($element) && multi_array_iskanje($search_for, $element)) ){
            return true;
        }
    }
    return false;
}

function generirajLadjo($dolzina, $sirina, $indeksladje) 
{
    do {
        $ladjicaROW = rand(1,10)*10-1;
        $ladjicaCOL = rand(1,10);
        $zacetniPolozaj = $ladjicaROW + $ladjicaCOL;

        for($sir = 0; $sir < $sirina; $sir++) {
            $HaliV = rand(0,1);
            if($HaliV == 1) {
                if($ladjicaCOL > $dolzina) {
                    for($x = 0; $x < $dolzina; $x++) {
                        $_SESSION["ladjica".strval($indeksladje)][$x] = $zacetniPolozaj - $x;
                    }
                } else {
                    for($x = 0; $x < $dolzina; $x++) {
                        $_SESSION["ladjica".strval($indeksladje)][$x] = $zacetniPolozaj + $x;
                    }
                }
            } else {
                if(($ladjicaROW > ($dolzina*10)) && $ladjicaROW % 10 != 0) {
                    for($x = 0; $x < $dolzina; $x++) {
                        $_SESSION["ladjica".strval($indeksladje)][$x] = $zacetniPolozaj - ($x*10);
                    }
                } else {
                    for($x = 0; $x < 5; $x++) {
                        $_SESSION["ladjica".strval($indeksladje)][$x] = $zacetniPolozaj + ($x*10);
                    }
                }
            }
        }
        $x--;
    } while(multi_array_iskanje($_SESSION["ladjica".strval($indeksladje)][$x], $_SESSION["ladjica"])==true);

}  


generirajLadjo(5, 1, 1);
generirajLadjo(4, 1, 2);
generirajLadjo(3, 1, 3);
generirajLadjo(3, 1, 4);
generirajLadjo(2, 1, 5);

Its a little dodgy controlling an outer loop with the result of something else going on in the loop IMO