Namespace declaration syntax in PHP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this PHP code with namespaces?

Consider the following PHP code. What will it output when run?

PHP

<?php
namespace MyApp\Utils;

function greet() {
    return "Hello from Utils!";
}

namespace MyApp\Main;

function greet() {
    return "Hello from Main!";
}

use function MyApp\Utils\greet as utilsGreet;

echo greet() . " and " . utilsGreet();

A Hello from Utils! and Hello from Utils!

B Hello from Utils! and Hello from Main!

C Hello from Main! and Hello from Main!

D Hello from Main! and Hello from Utils!

💡 Hint

Remember that the code after the second namespace declaration is in MyApp\Main namespace.

The first greet() call is in MyApp\Main namespace, so it calls MyApp\Main\greet(). The second call uses the alias utilsGreet which points to MyApp\Utils\greet().

❓ Predict Output

intermediate

What error does this PHP namespace code produce?

What error will this PHP code produce when run?

PHP

<?php
namespace MyApp\Tools;

function tool() {
    return "Tool function";
}

A No error, outputs nothing

B Fatal error: Cannot redeclare namespace

C Parse error: syntax error, unexpected 'function' (missing semicolon after namespace)

D Warning: namespace not found

💡 Hint

Check the syntax after the namespace declaration line.

The namespace declaration line must end with a semicolon or a block. Missing semicolon causes a parse error.

❓ Predict Output

advanced

What is the output of this PHP code with multiple namespace declarations?

What will this PHP code output when executed?

PHP

<?php
namespace A {
    const VALUE = 1;
}

namespace B {
    const VALUE = 2;
}

namespace {
    echo A\VALUE . "," . B\VALUE;
}

A 1,2

B 2,1

C VALUE,VALUE

D Parse error

💡 Hint

Constants in namespaces are accessed with backslash and namespace name.

The code prints the VALUE constant from namespace A and then from namespace B separated by a comma.

❓ Predict Output

advanced

What is the output of this PHP code using namespace and class?

What will this PHP code output when run?

PHP

<?php
namespace Outer\Inner;

class Test {
    public function message() {
        return "Inside Inner";
    }
}

namespace Outer;

class Test {
    public function message() {
        return "Inside Outer";
    }
}

namespace {
    $obj1 = new Outer\Test();
    $obj2 = new Outer\Inner\Test();
    echo $obj1->message() . " and " . $obj2->message();
}

A Inside Inner and Inside Outer

B Inside Outer and Inside Inner

C Fatal error: Class not found

D Parse error

💡 Hint

Classes in different namespaces can have the same name.

The code creates objects from two different namespaces and calls their message methods, printing both results.

❓ Predict Output

expert

What is the output of this PHP code with nested namespaces and use statements?

What will this PHP code output when executed?

PHP

<?php
namespace Alpha\Beta {
    class Sample {
        public function getName() {
            return "Alpha\\Beta";
        }
    }
}

namespace Alpha {
    use Alpha\Beta\Sample as BetaSample;

    class Sample {
        public function getName() {
            return "Alpha";
        }

        public function getBetaName() {
            $obj = new BetaSample();
            return $obj->getName();
        }
    }
}

namespace {
    $obj = new Alpha\Sample();
    echo $obj->getName() . " and " . $obj->getBetaName();
}

A Alpha and Alpha\Beta

B Alpha\Beta and Alpha

C Fatal error: Class not found

D Parse error

💡 Hint

The use statement imports Alpha\Beta\Sample as BetaSample inside Alpha namespace.

The Alpha\Sample class calls its own getName() and also creates an object of BetaSample (which is Alpha\Beta\Sample) to get its name.