Dynamic update statement - prepared statement - php

Question

I am generating my MYSQL update statement dynamically in PHP. As I want my application to be secure to SQL injections I want to use the prepared statement function. But as I'm pretty experienced I'm struggling to do so. Below my code so far:
function sqlUpdate($tablename)
{
$connect = sqlConnect();
$updateString = "UPDATE " . $tablename . " SET ";
$columnname = getColumnname($tablename, false, true);
for ($k=0; $k<count($columnname, COUNT_RECURSIVE); $k++)
{
if ($k+1 < count($columnname, COUNT_RECURSIVE))
{
$updateString .= $columnname[$k] . " = '" . mysqli_real_escape_string($connect, $_POST[$columnname[$k]]) . "', ";
}
else
{
$updateString .= $columnname[$k] . " = '" . mysqli_real_escape_string($connect, $_POST[$columnname[$k]]) . "' WHERE " . $columnname[0] . " = '" . mysqli_real_escape_string($connect, $_POST[$columnname[0]]) . "';";
}
}
if(mysqli_query($connect, $updateString))
{
echo "Daten wurden erfolgreich aktualisiert! </br>";
}
else
{
echo "Es ist ein Fehler aufgetreten... </br>";
}
mysqli_close($connect);
}
My code is working fine at the moment but I'm not managing to get it to work with prepared statements. I hope my question is not too stupid. Can somebody share some thoughts how to realize it with my code or do I have to completly overthink my approach?
Sorry again for my noob question...
Thanks!

Answer 1

Thanks to everybody who answered I managed to get it to work. I used the call_user_func_array function and can now generate the prepared statements for UPDATE and INSERT in one function:
function preparedStatement($tableName, $action)
{
$connect = sqlConnect();
$stmt = $connect->stmt_init();
$columnname = getColumnname($tableName, false, true);
for ($k=0; $k<count($columnname, COUNT_RECURSIVE); $k++)
{
$fielddata[] = $columnname[$k];
$fieldvalue[] = $_POST[$columnname[$k]];
}
if ($action == "insert")
{
$fieldvalue[0] = " ";
}
$fieldvalue_join = implode(',', array_map('addquote', $fieldvalue));
$fieldvalue = explode(",",$fieldvalue_join);
$valueCount = count($fieldvalue);
$question_mark = array();
for($i=0; $i<$valueCount; $i++)
{
$question_mark[] = '?';
}
$join_question_mark = implode(",", $question_mark);
$types = '';
foreach($fieldvalue as $param)
{
if(is_int($param))
{
$types .= 'i'; //integer
}
elseif (is_float($param))
{
$types .= 'd'; //double
}
elseif (is_string($param))
{
$types .= 's'; //string
}
else
{
$types .= 'b'; //blob and unknown
}
}
if ($action == "insert")
{
$insertString = "INSERT INTO ".$tableName."(".implode(",",$fielddata).") VALUES (".$join_question_mark.");";
$stmt->prepare($insertString);
$bind_names[] = $types;
}
elseif ($action == "update")
{
$updateString = "UPDATE " . $tableName . " SET ";
for ($k=0; $k<count($columnname, COUNT_RECURSIVE); $k++)
{
if ($k+1 < count($columnname, COUNT_RECURSIVE))
{
$updateString .= $columnname[$k] . " = ?, ";
}
else
{
$updateString .= $columnname[$k] . " = ? WHERE " . $columnname[0] . " = '" . mysqli_real_escape_string($connect, $_POST[$columnname[0]]) . "';";
}
}
$stmt->prepare($updateString);
$bind_names[] = $types;
}
for ($i=0; $i<count($fieldvalue); $i++)
{
$bind_name = 'bind' . $i;
$$bind_name = $fieldvalue[$i];
$bind_names[] = &$$bind_name;
}
call_user_func_array(array($stmt,'bind_param'),$bind_names);
if($stmt->execute())
{
$insert_id=$stmt->insert_id;
$stmt->close();
return $insert_id;
}
else
{
echo "Fehler beim Ausführen der Aktion...";
}
}
function addquote($str)
{
if($str[0]=="'" || $str[0]=='"' && $str[strlen($str)-1]=="'" || $str[strlen($str)-1]=="'" )
{
$str=substr($str,1);
$str=substr($str,0,-1);
}
return sprintf("%s", $str);
}