Why is my PDO prepared statement returning double results when fetching data into a CSV file?

PDO Prepared Statement Fetching Double Results

A user has encountered an issue where their PDO prepared statement is returning double results when outputting data to a CSV file. The code in question utilizes the $result_get_rows->fetch() function to retrieve the rows from the database.

Understanding the Fetch() Method

The fetch() method of a PDOStatement object is used to retrieve rows from a result set. By default, it returns rows as both indexed arrays (by column number) and associative arrays (by column name).

Resolving the Issue

To rectify the double results, it is recommended to specify how the result rows should be returned using the fetch_style parameter of the fetch() method. This parameter accepts one of the following constants:

• PDO::FETCH_ASSOC: Returns an associative array indexed by column name.
• PDO::FETCH_NUM: Returns an indexed array indexed by column number.
• PDO::FETCH_BOTH (default): Returns an array indexed by both column name and column number.

Modified Code

By using PDO::FETCH_ASSOC, the code can be modified as follows:

<code class="php">while ($rows_get_rows = $result_get_rows->fetch(PDO::FETCH_ASSOC)) {
  $csv .= '"'.join('","', str_replace('"', '""', $rows_get_rows))."\"\n";
}</code>

This modification will ensure that the rows are returned as associative arrays, effectively preventing the duplication of values when outputting to the CSV file.

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