How to Efficiently Determine Row Counts in PHP with PDO?

Determining Row Count with PDO

When working with PHP and PDO, it is essential to choose the optimal method for retrieving row counts. While mysql_num_rows was commonly used before PDO, this approach is not always ideal for large datasets.

The preferred solution when only the number of rows is required is to utilize the database's counting functionality. This can be achieved with a query like the following:

$sql = "SELECT count(*) FROM `table` WHERE foo = ?";
$result = $con->prepare($sql);
$result->execute([$bar]);
$number_of_rows = $result->fetchColumn();

However, if both the row count and the retrieved data are needed, PDO provides PDOStatement::rowCount() for buffered queries.

It is important to note that rowCount() may not be reliable across all drivers. For non-MySQL databases, it is recommended to use a query like SELECT COUNT(*) FROM table and retrieve the value using PDO::query()->fetchColumn().

Another option is to fetch all rows into an array using PDO::fetchAll() and then use count() to determine the number of rows.

For queries without variables, the query() function can be used instead of the prepared statement approach:

$nRows = $pdo->query('select count(*) from blah')->fetchColumn();
echo $nRows;

By choosing the appropriate method based on the specific requirements, developers can efficiently obtain row counts while maximizing performance in their PHP applications.

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