stmtfetchAllPDO

stmtfetchAllPDO refers to the fetchAll method of a PDOStatement in PHP's PDO extension. It retrieves all remaining rows from a previously executed query and returns them as an array. By default, if no fetch style is provided, fetchAll uses a mixed structural format, commonly including both associative and numeric indices for each row (PDO::FETCH_BOTH), but the exact shape depends on the chosen fetch style.

The method signature accepts three parameters: fetch_style, fetch_argument, and ctor_args. The fetch_style determines how rows are returned. Common options include:

- PDO::FETCH_ASSOC: each row as an associative array keyed by column name.

- PDO::FETCH_NUM: each row as a numeric array indexed by column number.

- PDO::FETCH_BOTH: each row includes both associative and numeric indices.

- PDO::FETCH_OBJ: each row as an anonymous object with properties matching column names.

- PDO::FETCH_COLUMN: returns a single column; fetch_argument selects the column index or name.

- PDO::FETCH_CLASS: returns instances of a specified class; fetch_argument is the class name, and ctor_args supplies constructor arguments.

Usage examples:

- Retrieve all rows as associative arrays: $rows = $stmt->fetchAll(PDO::FETCH_ASSOC);

- Retrieve a single column: $ids = $stmt->fetchAll(PDO::FETCH_COLUMN, 0);

- Retrieve as objects of a class: $users = $stmt->fetchAll(PDO::FETCH_CLASS, 'User', array('defaultRole'));

Performance and memory considerations:

fetchAll loads all remaining rows into memory. For large result sets, this can consume substantial memory. In such cases, iterating with fetch in a loop or streaming results is preferable.

Notes:

If no rows remain, fetchAll returns an empty array. Error handling depends on the PDO error mode; in exception mode, errors raise exceptions. Some drivers may have limitations on certain fetch styles.