PHP Declaring sub-namespaces

PHP allows creating nested namespaces, similar to how directories contain subdirectories in a file system. Sub-namespaces are declared using the backslash character \ to define the hierarchical relationship between parent and child namespaces.

Syntax

To declare a sub-namespace, use the following syntax ?

namespace ParentNamespace\ChildNamespace;

Example

Here's how to create and use sub-namespaces with functions ?

<?php
namespace myspace\space1;
function hello() {
    echo "Hello World from space1
";
}

namespace myspace\space2;
function hello(){
    echo "Hello World from space2
";
}

// Using fully qualified names
myspace\space1\hello();
myspace\space2\hello();
?>

Hello World from space1
Hello World from space2

Using the 'use' Keyword

You can import sub-namespaces with the use keyword for cleaner code ?

<?php
namespace myspace\space1;
function greet() {
    echo "Greetings from space1
";
}

namespace myspace\space2;
function greet() {
    echo "Greetings from space2
";
}

use myspace\space1 as s1;
use myspace\space2 as s2;

s1\greet();
s2\greet();
?>

Greetings from space1
Greetings from space2

Multiple Levels

Sub-namespaces can be nested to multiple levels ?

<?php
namespace company\department\team;
function work() {
    echo "Working in team namespace
";
}

namespace company\department\management;
function manage() {
    echo "Managing from management namespace
";
}

company\department\team\work();
company\department\management\manage();
?>

Working in team namespace
Managing from management namespace

Conclusion

Sub-namespaces provide hierarchical organization for PHP code, using backslashes to separate levels. Use fully qualified names or the use keyword with aliases for cleaner access to nested namespace elements.