如何将字符串插入数据库表中的不同列？

Basically I've made an string out of pdf file, and that string contains comma-separated values which I now need to insert into different columns in table. I would try similar question's answer here, but I don't get it for my need.

I already tried exploding that string into an array, so that comma is each element separator like so:

$array = explode(',', $text);

But since I have just 3 columns into table, I need to sort that values into those columns, so that each third string would go into first column and all following it into following columns. I tried doing it like so:

$duzina=count($array);
        for($i=0;$i<$duzina;$i++) {
            if ($i = 0 && $i < 3) {
                $mysqli->query("INSERT INTO `test` (`name`, `surname`, `email`) VALUES
                (
                    '" . trim($array[$i]) . "',
                    '" . addslashes($array[$i + 1]) . "',
                    '" . addslashes($array[$i + 2]) . "'
                )
            ");
            }
            if ($i/3 == 0) {// has found a 3rd,6th,9th element of an $array

                $mysqli->query("INSERT INTO `test` (`name`, `surname`, `email`) VALUES
                (
                    '" . trim($array[$i]) . "',
                    '" . addslashes($array[$i + 1]) . "',
                    '" . addslashes($array[$i + 2]) . "'
                )
            ");
            } else {
                $mysqli->query("INSERT INTO `test` (`name`, `surname`, `email`) VALUES
                (
                    '" . trim($array[$i]) . "',
                    '" . addslashes($array[$i + 1]) . "',
                    '" . addslashes($array[$i + 2]) . "'
                )
            ");
            }

But all it does is inserting first 3 elements of $array. Please help

Use prepared statements.
Restructure your data to be meaningful in code(useful for debugging)
Loop wisely(increment by 3)

Note, code below is not fieldtested, just proof of concept.

$array = loadpdfwhatever();
$length = count($array);

// Restructure the raw data to be meaningful to a human. Can be skipped,
// but this will help you debugging in + 3 weeks from now :-)
$restructured = [];
for($i=0;$i<$length;$i+=3) { // note the $i+3 to increment by 3.
    $restructured[] = ['name'=> $array[$i],
                       'surname'=> $array[$i+1],
                       'email'=> $array[$i+2]];
}


// Using prepared statements we only have to build up the query once.
// Makes code faster and more efficient.
if ($stmt = mysqli_prepare($link, "INSERT INTO `test` (`name`, `surname`, `email`) VALUES ( ?, ?, ? ) ")) {
    foreach($restructured as $insert) {
        mysqli_stmt_bind_param($stmt,'sss',$insert['name'],
                                           $insert['surname'],
                                           $insert['email']); 
        mysqli_stmt_execute($stmt)
    }
}

no the rest of division get by % not /, so replace this:

if ($i/3 == 0) {

with

if ($i%3 == 0) {

2 things :

first use if / elseif /else

if ($i = 0 && $i < 3) {
    ...
}
elseif ($i%3 == 0) {
    ...
}
else
{
    ....
}

Second :

its $i%3 == 0 and not $i/ 3 == 0