I have the following code:

foreach ($_POST['arrachar'] as $selected) {
    $stringArrachar = "";
    for ($x  = 0; $x < count($arrayTypes); $x++) {
        if (isset($selected[$arrayTypes[$x]])) {
            $stringArrachar .= $selected[$arrayTypes[$x]] . ",";
            continue;
        }
        $stringArrachar .= ",";
    }
    $stringArrachar = substr($stringArrachar, 0, -1);
    $string = $stringArrachar;
    $vazio = str_replace(",", "", $string);
    $date = explode(",", $string);
    $data = $date[0];
    if ($vazio != "") {
        $stringSelect .= "SUBSTRING_INDEX(arrachar, ',', 1) = ? OR ";
        $arrayValues[] = array(
            "data" => $data,
            "arrachar" => $string
        );
    }
}
$stringSelect = substr($stringSelect, 0, -3);
$stmt = $conn->prepare($stringSelect);
$stmt->execute();

When running it generates the following error:

Fatal error: Uncaught PDOException: SQLSTATE[42000]: Syntax error or
access violation: 1064 You have an error in your SQL syntax; check the
manual that corresponds to your MySQL server version for the right
syntax to use near ‘? OR SUBSTRING_INDEX(arrachar, ‘,’, 1) = ? OR
SUBSTRING_INDEX(arrachar, ‘,’, 1) ‘

If you change this line in the code like this, it already works:

$stringSelect .= "SUBSTRING_INDEX(arrachar, ',', 1) = '$data' OR ";

Can you help?