Aliasing with as keyword in PHP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of aliased class usage

What is the output of this PHP code using aliasing with the as keyword?

PHP

<?php
namespace Animals;
class Dog {
    public function speak() {
        return "Woof!";
    }
}

namespace Pets;
use Animals\Dog as PetDog;

$dog = new PetDog();
echo $dog->speak();
?>

A Woof!

B Fatal error: Class 'Pets\Dog' not found

C Woof Woof!

D Error: Cannot use 'as' outside namespace

💡 Hint

Look at how the use statement renames the class from another namespace.

The use Animals\Dog as PetDog; statement creates an alias PetDog for Animals\Dog. So, new PetDog() creates an instance of Animals\Dog. Calling speak() returns 'Woof!'.

❓ Predict Output

intermediate

Aliasing function import output

What will this PHP code output when using aliasing with the as keyword for functions?

PHP

<?php
namespace Utils;
function greet() {
    return "Hello!";
}

namespace Main;
use function Utils\greet as sayHello;

echo sayHello();
?>

A Hello!

B Fatal error: Call to undefined function sayHello()

C Syntax error: unexpected 'as'

D Hello Hello!

💡 Hint

Check how the function is imported with an alias.

The use function Utils\greet as sayHello; imports the function greet from the Utils namespace and aliases it as sayHello. Calling sayHello() runs Utils\greet() and returns 'Hello!'.

🔧 Debug

advanced

Identify the error in aliasing a constant

This PHP code tries to alias a constant using the as keyword. What error will it produce?

PHP

<?php
namespace Config;
const VERSION = '1.0';

namespace App;
use const Config\VERSION as APP_VERSION;

echo APP_VERSION;
?>

A Fatal error: Undefined constant APP_VERSION

B Fatal error: Cannot use 'as' with const

C Parse error: syntax error, unexpected 'as'

D 1.0

💡 Hint

PHP supports aliasing constants with use const and as.

The code correctly aliases the constant VERSION from Config namespace as APP_VERSION. Echoing APP_VERSION outputs '1.0'. No error occurs.

📝 Syntax

advanced

Which aliasing syntax is invalid?

Which of the following PHP aliasing statements using as keyword is NOT valid syntax?

A use Some\Namespace\ClassName as AliasName;

B use Some\Namespace\ClassName alias ClassAlias;

C use const Some\Namespace\CONST_NAME as AliasConst;

D use function Some\Namespace\funcName as aliasFunc;

💡 Hint

Check the correct keyword order and syntax for aliasing.

Option B is invalid because the correct syntax uses the as keyword, not the word 'alias'. The correct form is use Some\Namespace\ClassName as ClassAlias;.

🚀 Application

expert

Predict the output with multiple aliasing

Given this PHP code with multiple aliasing, what will be the output?

PHP

<?php
namespace A {
    class Test {
        public function msg() {
            return "From A";
        }
    }
}

namespace B {
    class Test {
        public function msg() {
            return "From B";
        }
    }
}

namespace Main {
    use A\Test as TestA;
    use B\Test as TestB;

    $a = new TestA();
    $b = new TestB();

    echo $a->msg() . ' & ' . $b->msg();
}
?>

A Parse error: syntax error, unexpected 'use'

B From B & From A

C From A & From B

D Fatal error: Cannot redeclare class Test

💡 Hint

Aliasing allows using two classes with the same name from different namespaces.

The code aliases A\Test as TestA and B\Test as TestB. Creating objects and calling msg() returns 'From A' and 'From B' respectively, joined by ' & '.