Manual includes vs autoloading in PHP - Practice Questions

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of manual include vs autoloading

What will be the output of this PHP code snippet that uses manual includes and autoloading?

PHP

<?php
// File: classes/Foo.php

// File: autoload.php
spl_autoload_register(function ($class) {
    include 'classes/' . $class . '.php';
});

include 'classes/Foo.php';
$foo1 = new Foo();
echo $foo1->sayHello() . "\n";

$foo2 = new Bar();
echo $foo2->sayHello() . "\n";

// File: classes/Bar.php
?>

A Hello from Bar!\nHello from Foo!\n

B Hello from Foo!\nFatal error: Uncaught Error: Class 'Bar' not found

C Hello from Foo!\nHello from Bar!\n

D Fatal error: Uncaught Error: Class 'Foo' not found

💡 Hint

Remember that manual include loads Foo.php before creating Foo, and autoload triggers for Bar class.

The manual include loads Foo.php so Foo class is available. When Bar is instantiated, autoload triggers and includes Bar.php automatically, so both classes exist and their methods run correctly.

❓ Predict Output

intermediate

What error occurs without autoloading?

What error will this PHP code produce if autoloading is not set up and only Foo.php is manually included?

PHP

<?php
include 'classes/Foo.php';
$foo = new Foo();
echo $foo->sayHello() . "\n";
$bar = new Bar();
echo $bar->sayHello() . "\n";
?>

A Hello from Foo!\nHello from Bar!\n

B Fatal error: Uncaught Error: Class 'Bar' not found

C Fatal error: Uncaught Error: Class 'Foo' not found

D Parse error: syntax error, unexpected 'Bar' (T_STRING)

💡 Hint

Think about what happens when PHP tries to create an object of a class that was never included or autoloaded.

Since Bar.php was never included and no autoload function is registered, PHP cannot find the Bar class and throws a fatal error.

🔧 Debug

advanced

Why does autoload fail to load class?

Given this autoload function, why does instantiating class Baz fail with a fatal error?

PHP

<?php
spl_autoload_register(function ($class) {
    include 'lib/' . strtolower($class) . '.php';
});

$baz = new Baz();
echo $baz->greet();

// File: lib/Baz.php
?>

A The class Baz is not defined in the included file.

B The autoload function is missing a return statement.

C The spl_autoload_register function is called after the class instantiation.

D The filename is Baz.php but autoload tries to include baz.php, which does not exist (case-sensitive filesystem).

💡 Hint

Check how the filename is constructed in the autoload function and consider case sensitivity.

The autoload function converts the class name to lowercase, so it tries to include 'lib/baz.php'. On case-sensitive systems, 'Baz.php' and 'baz.php' are different files, so include fails and class Baz is not found.

📝 Syntax

advanced

Identify the syntax error in autoload function

Which option contains the correct syntax for registering an autoload function in PHP?

A spl_autoload_register(function ($class) { include 'classes/' . $class . '.php'; });

B spl_autoload_register(function ($class) { include 'classes/' . $class . '.php' });

C spl_autoload_register(function($class) include 'classes/' . $class . '.php';);

D spl_autoload_register(function $class { include 'classes/' . $class . '.php'; });

💡 Hint

Remember the syntax for anonymous functions requires parentheses around parameters and braces around the body.

Option A correctly uses parentheses around the parameter and braces around the function body. Option A misses parentheses around parameter, B misses semicolon inside braces, C misses braces.

🚀 Application

expert

How many files are included during execution?

Consider this PHP script with manual includes and autoloading. How many files are included when the script runs?

PHP

<?php
include 'classes/Foo.php';
spl_autoload_register(function ($class) {
    include 'classes/' . $class . '.php';
});
$foo = new Foo();
$bar = new Bar();
baz();
function baz() {
    $baz = new Baz();
    echo $baz->sayHello();
}
// Files:
// classes/Foo.php defines class Foo
// classes/Bar.php defines class Bar
// classes/Baz.php defines class Baz
?>

A 3

B 2

C 1

D 0

💡 Hint

Count manual includes plus autoload triggered includes for Bar and Baz classes.

The script manually includes Foo.php. Then autoload triggers for Bar and Baz classes, including Bar.php and Baz.php. Total files included: 3.