Fetch modes and styles in PHP - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the default fetch mode in PHP's PDO when retrieving data?

The default fetch mode is PDO::FETCH_BOTH, which returns an array indexed by both column name and number.

beginner

Explain PDO::FETCH_ASSOC fetch mode.

PDO::FETCH_ASSOC returns an array indexed by column names only, which helps avoid duplicate data and is memory efficient.

intermediate

What does PDO::FETCH_OBJ do when fetching data?

It returns each row as an anonymous object where columns are accessible as properties, e.g., $row->columnName.

intermediate

How does PDO::FETCH_CLASS differ from other fetch modes?

It fetches data into an instance of a specified class, mapping columns to class properties, allowing object-oriented data handling.

intermediate

What is the purpose of PDO::FETCH_COLUMN?

It fetches only a single column from the next row in the result set, useful when you need just one column's data.

Which fetch mode returns data as an object with properties matching column names?

A PDO::FETCH_COLUMN

B PDO::FETCH_ASSOC

C PDO::FETCH_NUM

D PDO::FETCH_OBJ

PDO::FETCH_OBJ returns each row as an object with properties named after the columns.

If you want to fetch data as an array indexed by column names only, which fetch mode should you use?

A PDO::FETCH_BOTH

B PDO::FETCH_NUM

C PDO::FETCH_ASSOC

D PDO::FETCH_CLASS

PDO::FETCH_ASSOC returns an associative array indexed by column names.

What does PDO::FETCH_NUM return?

A An array indexed by column numbers

B A class instance

C An object with column properties

D An array indexed by column names

PDO::FETCH_NUM returns an array indexed by column numbers (0-based).

Which fetch mode allows you to fetch data directly into a user-defined class?

A PDO::FETCH_OBJ

B PDO::FETCH_CLASS

C PDO::FETCH_ASSOC

D PDO::FETCH_COLUMN

PDO::FETCH_CLASS maps the row data into an instance of a specified class.

When would you use PDO::FETCH_COLUMN?

A To fetch a single column from each row

B To fetch data as an object

C To fetch all columns as an associative array

D To fetch data as a numeric array

PDO::FETCH_COLUMN fetches only one column from each row, useful for lists of values.

Describe the main differences between PDO::FETCH_ASSOC, PDO::FETCH_NUM, and PDO::FETCH_BOTH.

Think about how the data is indexed in the returned array.

Explain how PDO::FETCH_CLASS can be used to work with database results in an object-oriented way.

Consider how this fetch mode helps organize data as objects.