Why Does PDO Return Only One Row When Binding Parameters to a WHERE IN Clause?

Binding WHERE IN Clause Parameters with PDO

Question:

When attempting to bind parameters to a WHERE IN clause using PDO, the resulting count is always one, unlike when manually inserting values without parametrization. What is the cause of this discrepancy?

Code:

$myArray = implode($myArray, ',');
$sth = $dbh->prepare('SELECT foo FROM bar WHERE ids IN (:ids)');
$sth->bindParam(':ids', $myArray);
$sth->execute();
$result = $sth->fetch();
echo $sth->rowCount();

Answer:

Unfortunately, PHP Data Objects (PDO) does not support binding parameters for IN clauses directly. The $myArray array is treated as a single string, similar to this SQL:

SELECT foo FROM bar WHERE ids IN ('1,2,3')

Despite the presence of multiple comma-separated values, the database interprets them as one string value.

To achieve the desired behavior, the IN clauses must be manually inserted into the query as follows:

'SELECT foo FROM bar WHERE ids IN (' . $myArray .')'

Unfortunately, there is no alternative mechanism for parameter binding in PDO's IN clauses at this time.

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