How does the keyword use work in PHP and can I import classes with it

Question

I have a file with a class Resp  The path is   C  xampp htdocs One Classes Resp php   And I have an index php file in this directory   C  xampp htdocs Two Http index php   In this index php file I want to instantiate a class Resp    a   new Resp      I know I can use require or include keywords to include the file with a class   require  One Classes Resp php             I ve set the include path correctly already   C  xampp htdocs   It works   a   new Resp      But I want to import classes without using require or include  I m trying to understand how use keyword works  I tried theses steps but nothing works   use One Classes Resp  use xampp htdocs One Classes Resp  use htdocs One Classes Resp  use One Classes  use htdocs One Classes        nothing works      a   new Resp      It says   Fatal error  Class  One Classes Resp  not found in C  xampp htdocs Two Http index php   How does the keyword use work  Can I use it to import classes

User · Answer

The issue is most likely you will need to use an auto loader that will take the name of the class (break by '\' in this case) and map it to a directory structure.

You can check out this article on the autoloading functionality of PHP. There are many implementations of this type of functionality in frameworks already.

I've actually implemented one before. Here's a link.

User · Answer

Can I use it to import classes    You can t do it like that besides the examples above  You can also use the keyword use inside classes to import traits  like this   trait Stuff       private  baz    baz       public function bar             return  this- gt baz           class Cls       use Stuff      import traits like this     foo   new Cls  echo  foo- gt bar       spits out  baz

User · Answer

I agree with Green  Symfony needs namespace  so why not use them    This is how an example controller class starts      namespace Acme DemoBundle Controller       use Symfony Bundle FrameworkBundle Controller Controller       class WelcomeController extends Controller

User · Answer

use doesn t include anything  It just imports the specified namespace  or class  to the current scope  If you want the classes to be autoloaded - read about autoloading

User · Answer

The use keyword is for aliasing in PHP and it does not import the classes  This really helps  1  When you have classes with same name in different namespaces 2  Avoid using really long class name over and over again

User · Answer

No  you can not import a class with the use keyword  You have to use include require statement  Even if you use a PHP auto loader  still autoloader will have to use either include or require internally     The Purpose of use keyword   Consider a case where you have two classes with the same name  you ll find it strange  but when you are working with a big MVC structure  it happens  So if you have two classes with the same name  put them in different namespaces  Now consider when your auto loader is loading both classes  does by require   and you are about to use object of class  In this case  the compiler will get confused which class object to load among two  To help the compiler make a decision  you can use the use statement so that it can make a decision which one is going to be used on   Nowadays major frameworks do use include or require via composer and psr  1  composer   2  PSR-4 autoloader  Going through them may help you further   You can also use an alias to address an exact class  Suppose you ve got two classes with the same name  say Mailer with two different namespaces   namespace SMTP  class Mailer     and   namespace Mailgun  class Mailer     And if you want to use both Mailer classes at the same time then you can use an alias    use SMTP Mailer as SMTPMailer  use Mailgun Mailer as MailgunMailer    Later in your code if you want to access those class objects then you can do the following    smtp mailer   new SMTPMailer   mailgun mailer   new MailgunMailer    It will reference the original class   Some may get confused that then of there are not Similar class names then there is no use of use keyword  Well  you can use   autoload  class  function which will be called automatically when use statement gets executed with the class to be used as an argument and this can help you to load the class at run-time on the fly as and when needed    Refer this answer to know more about class autoloader

User · Answer

Don   t overthink what a Namespace is   Namespace is basically just a Class prefix  like directory in Operating System  to ensure the Class path uniqueness   Also just to make things clear  the use statement is not doing anything only aliasing your Namespaces so you can use shortcuts or include Classes with the same name but different Namespace in the same file   E g      You can do this at the top of your Class use Symfony Component Debug Debug   if    SERVER  APP DEBUG             So you can utilize the Debug class it in an elegant way     Debug  enable           Instead of this ugly one         Symfony Component Debug Debug  enable        If you want to know how PHP Namespaces and autoloading  the old way as well as the new way with Composer  works  you can read the blog post I just wrote on this topic  https   enterprise-level-php com 2017 12 25 the-magic-behind-autoloading-php-files-using-composer html

User · Answer

You ll have to include require the class anyway  otherwise PHP won t know about the namespace  You don t necessary have to do it in the same file though  You can do it in a bootstrap file for example   or use an autoloader  but that s not the topic actually

User · Answer

Using the keyword  use  is for shortening namespace literals  You can use both with aliasing and without it  Without aliasing you must use last part of full namespace    lt  php     use foo bar lastPart       obj new lastPart AnyClass      If there s not the line above  a fatal error will be encountered    gt

User · Answer

Namespace is use to define the path to a specific file containing a class e g   namespace album className    class className    enter class properties and methods here     You can then include this specific class into another php file by using the keyword  use  like this   use album className   class album extends classname     enter class properties and methods     NOTE  Do not use the path to the file containing the class to be implements  extends of use to instantiate an object but only use the namespace

[php] How does the keyword "use" work in PHP and can I import classes with it?

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