PDO MySQL Error - SQLSTATE [42000]: by UPDATE(ING) integer to table - mysql

Question

I can update text strings (varchar) types to my Mysql database with PDO without any problems. but with integer (int(11)) types - my PDOstatement has some big problems and also can not write the integer value to the database.
here you can see the error message I get by putting integer values for UPDATE:
ERRNO:42000 ERROR: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 'age = '800' WHERE id = '1'' at line 1
I am getting the values from $_POST like this:
foreach ($_POST['changed'] as $SubArray) {
foreach ($SubArray as $key => $value) {
if ($key === 'recid') continue;
$sql = "UPDATE clients SET $key = :value WHERE id = :recid";
$STH = $DBH->prepare($sql);
try {
$STH->execute(array(':value' => $value, ':recid' => $SubArray['recid']));
} catch (PDOException $e) {
$code = $e->getCode();
$file = $e->getFile();
$line = $e->getLine();
$msg = $e->getMessage();
echo "$file:$line ERRNO:$code ERROR:$msg";
}
}
}
echo urlencode($sql) => UPDATE+clients+SET+age+%3D+%3Avalue+WHERE+id+%3D+%3Arecid

Answer 1

setting up the query ($sql) like this, does the trick.
$sql = "UPDATE `clients` SET `$key` = :value WHERE id = :recid";
before and after table and column name use backticks
`