How to Efficiently Retrieve the Row Count from a PHP PDO SELECT Query?

Retrieving Row Count in PHP PDO

Unlike MySQLi's num_rows variable, PHP PDO lacks a straightforward method for determining the number of rows yielded by a SELECT query. This leads to the question, is there an alternative approach to counting rows without resorting to count($results->fetchAll())?

PDO's rowCount Method

The PDO specification includes a PDOStatement->rowCount method; however, it is generally discouraged for use in this context due to inconsistencies across different databases. As noted in the manual, rowCount typically fails to provide an accurate count when applied to SELECT statements.

Recommended Approach

To avoid potential errors, the preferred method for counting rows in PHP PDO is to issue a separate SELECT COUNT(*) statement with the same constraints as your intended SELECT query. Subsequently, use PDOStatement::fetchColumn() to retrieve the row count. This process ensures a reliable and cross-database compatible approach.

Alternative Option for Existing Recordsets

If you already possess a recordset and need to determine its row count, you can fetch the data using one of the fetch* methods and utilize PHP's count function. While this approach is straightforward, it requires fetching the entire recordset into memory, which may not be efficient for large datasets.

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