Global namespace access in PHP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of accessing global namespace function

What is the output of this PHP code?

PHP

<?php
namespace MyApp;
function strlen($str) {
    return "MyApp strlen: " . strlen($str);
}

echo strlen("test");
echo "\n";
echo \strlen("test");
echo "\n";
echo \MyApp\strlen("test");
?>

A

MyApp strlen: 4
4
4

B

MyApp strlen: 4
4
MyApp strlen: 4

C

4
4
MyApp strlen: 4

D

4
MyApp strlen: 4
4

💡 Hint

Remember that \strlen calls the global function, while strlen inside namespace calls the local one.

Inside the namespace MyApp, strlen() is redefined. Calling strlen("test") calls the local function, which prefixes output. Calling \strlen("test") calls the global PHP strlen function. Calling \MyApp\strlen("test") calls the namespaced function explicitly.

❓ Predict Output

intermediate

Accessing global constant inside namespace

What will this PHP code output?

PHP

<?php
namespace Test;
const PI = 3.14;

echo PI . "\n";
echo \PI . "\n";
?>

A

3.14
Fatal error: Uncaught Error: Undefined constant PI

B

3.14
PHP Notice: Undefined constant PI

C

3.14
1

D

3.14
3.14

💡 Hint

Global constants are not automatically imported into namespaces.

Inside the namespace Test, PI refers to Test\PI which is defined as 3.14. \PI tries to access a global constant PI, which does not exist, causing a fatal error.

🔧 Debug

advanced

Why does this global function call fail?

This code throws an error. What is the cause?

PHP

<?php
namespace App;
function test() {
    echo "App test";
}

function run() {
    test();
    \test();
}

run();
?>

A Calling test() fails because it requires parentheses.

B Calling test() fails because it is ambiguous inside the namespace.

C Calling \test() fails because global functions cannot be called inside namespaces.

D Calling \test() fails because there is no global function named test.

💡 Hint

Check if the global namespace has a function named test.

Inside namespace App, test() calls App\test(), which exists. \test() tries to call the global test() function, which does not exist, causing a fatal error.

📝 Syntax

advanced

Which option correctly accesses a global class inside a namespace?

Given a global class Logger, which code correctly creates an instance inside namespace App?

PHP

<?php
namespace App;
class Logger {
    public function log() {
        echo "App Logger";
    }
}

// Global Logger class
class \Logger {
    public function log() {
        echo "Global Logger";
    }
}

// Which line correctly creates a global Logger instance?
// $logger = ???;
?>

A $logger = new \Logger();

B $logger = new Logger();

C $logger = new \App\Logger();

D $logger = new \global\Logger();

💡 Hint

Use a leading backslash to access global classes from inside a namespace.

Inside namespace App, Logger() refers to App\Logger. To access the global Logger class, use \Logger(). \App\Logger() is valid but redundant inside App namespace. \global\Logger() is invalid syntax.

🚀 Application

expert

How to call a global function named 'process' inside a namespace with a local function of the same name?

You have a global function process() and inside namespace Data you also have a function process(). How do you call the global process() from inside Data namespace?

PHP

<?php
function process() {
    return "global process";
}

namespace Data {
    function process() {
        return "Data process";
    }

    function run() {
        // Call global process here
        return ???;
    }
}

echo \Data\run();
?>

A process()

B global\process()

C \process()

D Data\process()

💡 Hint

Use a leading backslash to call global functions inside namespaces.

Inside namespace Data, process() calls Data\process(). To call the global process(), prefix with a backslash: \process(). global\process() is invalid syntax. Data\process() calls the local function.