versatile insertion method for PDO class - php

Question

this is my insertion method in PDO, it is working 100%. this 'insert' method accepts table, column and value but i want to make it versatile. (i want to insert values with or without the column names)
public function insert($table, $pair = array()){
try{
$Sql = "INSERT INTO $table ( ";
$Sql .= implode(", ", array_keys($pair));
$Sql .= " )";
$Sql .= " VALUES (";
$Sql .= implode(", ", array_fill("0", count($pair), " ?"));
$Sql .= " )";
$array = array_combine(array_keys(array_fill("1", count($pair), ":")), $pair);
$ready = $this->conn->prepare($Sql);
foreach($array as $key => $value)
{
$ready->bindValue($key, $value, PDO::PARAM_STR);
}
$ready->execute();
}
catch(Exception $e){
$this->trace .= " • ". $e->getMessage();
}
}
$new = new community();
echo $new->insert("table", array("Col1" => "value1", "col1" => "value1"));

Answer 1

There are two problems with your function.
It is vulnerable to SQL injection.
It is not flexible. Following the pattern, you are going to have a thousand functions of this kind, which will make your code into mess. Yet it would be always limited subset against real SQL.
What you really need is a function that can create a SET statement out of array and a list of allowed fields.
As a further improvement you may devise a custom placeholder for this statement.
Having these two things you can work out a single general purpose function to run all the DML queries like this:
$db->query("INSERT INTO t SET %u", array("Col1" => "value1", "col1" => "value1"));
It will cost you 3 additional words (insert, into and set), but it will be
readable. Everyone can understand SQL. While to read your function one need a documentation
flexible. It can support any queries and modifiers, not only one single-formed insert.
Every query you wish you can run with this single function:
$data = array("Col1" => "value1", "col1" => "value1");
$db->query("INSERT IGNORE INTO t SET %u", $data);
$db->query("REPLACE INTO t SET %u", $data);
$db->query("DELETE FROM t WHERE id = ?", $id);
// and so on
No dedicated functions actually needed.
Also, you have to always verify a set of fields against a hardcoded white list, to let a user insert only fields they are allowed to. Do not let a user to alter privileges, messages count and so on.
But even without custom placeholder it would require no set of SQL-mapped functions but just a function to create a SET and a general purpose query execution function:
$allowed = array("name","surname","email"); // allowed fields
$sql = "INSERT INTO users SET ".pdoSet($fields,$values);
$stm = $dbh->query($sql ,$values);