Fetch modes and styles in PHP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this PHP PDO fetch mode code?

Consider the following PHP code snippet using PDO to fetch data from a database. What will be the output of the print_r statement?

PHP

<?php
$pdo = new PDO('sqlite::memory:');
$pdo->exec("CREATE TABLE users (id INTEGER, name TEXT);");
$pdo->exec("INSERT INTO users VALUES (1, 'Alice'), (2, 'Bob');");
$stmt = $pdo->query("SELECT * FROM users WHERE id = 1");
$result = $stmt->fetch(PDO::FETCH_ASSOC);
print_r($result);
?>

A Array ( [id] => 1 [name] => Alice )

B Array ( [0] => 1 [1] => Alice )

C Array ( [id] => 1 [0] => 1 [name] => Alice [1] => Alice )

D NULL

💡 Hint

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

The fetch mode PDO::FETCH_ASSOC returns an array indexed by column names only, so the output contains keys 'id' and 'name' with their respective values.

❓ Predict Output

intermediate

What does this PHP PDO fetch style code output?

Given this PHP code using PDO, what will be the output of the print_r statement?

PHP

<?php
$pdo = new PDO('sqlite::memory:');
$pdo->exec("CREATE TABLE products (id INTEGER, name TEXT);");
$pdo->exec("INSERT INTO products VALUES (10, 'Pen'), (20, 'Pencil');");
$stmt = $pdo->query("SELECT * FROM products WHERE id = 20");
$result = $stmt->fetch(PDO::FETCH_NUM);
print_r($result);
?>

A Array ( [0] => 20 [1] => Pencil )

B Array ( [id] => 20 [name] => Pencil )

C Array ( [id] => 20 [0] => 20 [name] => Pencil [1] => Pencil )

D false

💡 Hint

PDO::FETCH_NUM returns a numeric array indexed by column numbers.

The fetch mode PDO::FETCH_NUM returns an array indexed by column numbers starting at 0, so the output contains keys 0 and 1 with values 20 and 'Pencil'.

❓ Predict Output

advanced

What is the output of this PHP PDO fetch with FETCH_OBJ?

Look at this PHP code using PDO with fetch mode FETCH_OBJ. What will be the output of the echo statement?

PHP

<?php
$pdo = new PDO('sqlite::memory:');
$pdo->exec("CREATE TABLE employees (id INTEGER, name TEXT);");
$pdo->exec("INSERT INTO employees VALUES (5, 'John');");
$stmt = $pdo->query("SELECT * FROM employees WHERE id = 5");
$result = $stmt->fetch(PDO::FETCH_OBJ);
echo $result->name;
?>

A Array

B John

C 5

D Notice: Trying to get property of non-object

💡 Hint

PDO::FETCH_OBJ returns an anonymous object with properties named after columns.

Using PDO::FETCH_OBJ returns an object where column names are properties. Accessing $result->name prints 'John'.

❓ Predict Output

advanced

What error does this PHP PDO fetch code produce?

What error will this PHP code produce when executed?

PHP

<?php
$pdo = new PDO('sqlite::memory:');
$pdo->exec("CREATE TABLE items (id INTEGER, name TEXT);");
$pdo->exec("INSERT INTO items VALUES (1, 'Book');");
$stmt = $pdo->query("SELECT * FROM items WHERE id = 1");
$result = $stmt->fetch(PDO::FETCH_CLASS);
echo $result->name;
?>

A Fatal error: Uncaught ArgumentCountError: PDO::fetch() expects at least 1 parameter

B Warning: PDO::fetch() expects parameter 1 to be int, string given

C Book

D Fatal error: Class name must be specified when using PDO::FETCH_CLASS

💡 Hint

PDO::FETCH_CLASS requires a class name as the second argument.

When using PDO::FETCH_CLASS, you must specify the class name as the second argument to fetch(). Omitting it causes a fatal error.

🧠 Conceptual

expert

Which fetch mode returns both numeric and associative keys?

In PHP PDO, which fetch mode returns an array containing both numeric indexes and associative keys for the columns?

A PDO::FETCH_NUM

B PDO::FETCH_ASSOC

C PDO::FETCH_BOTH

D PDO::FETCH_OBJ

💡 Hint

This fetch mode combines numeric and associative keys in the result array.

PDO::FETCH_BOTH returns an array indexed by both column names and column numbers, so you get both numeric and associative keys.