PDO bindValue problem

[spamyboy]

function update_user($user_id, $array) {
		$result	= $this->db->prepare("UPDATE `gcms_user`
									 SET ?=?
									 WHERE `user_id`=?;");
			$result->bindValue(3,	$user_id,	PDO::PARAM_INT);
		foreach ($array as $key=>$value) {
			$result->bindValue(1,	$key,		PDO::PARAM_STR); // Problem here
			$result->bindValue(2,	$value,		PDO::PARAM_STR);
			$result->execute();
		}
	}

Problem is basic. Query is generated like "UPDATE gcms_user SET 'key_or_1_var'='value_or_2_var' WHERE user_id='#id#';"
So basically key_or_1_var is taken as variable since it is with '' and how to change that to ``?

[laserlight]

I believe the binding is only to values, not column names, so what you are asking for is not possible. I reason that this is so because the choice of a different column could change the way the query should be evaluated, thus the statement must be prepared again.

[Weedpacket]

Doing multiple UPDATE statements when just one would to is extremely wasteful anyway.
Build the statement first (making an array $keys containing "$key=?" for each $key in array_keys($array)) and using "... SET ".join(',', $keys)." WHERE...") then prepare that and bind all of the values to it.