Can PHP namespaces contain variables?

Question

Can PHP namespaces contain variables? If so, how can this be accomplished?

Imperception

Have you tried? If you have tried, what was the outcome? – Redress

@Redress Or he could ask, get a proper answer and help future readers with it... instead of everyone having to "try it out" themselves. – Richy

Answer 1

No. You can set a variable after declaring a namespace, but variables will always exist in the global scope. They are never bound to namespaces. You can deduce that from the absence of any name resolution descriptions in

• FAQ: things you need to know about namespaces (PHP 5 >= 5.3.0)

There would also be no allowed syntax to locate variables in a namespace.

print \namespace\$var;      // syntax error

print "${namespace\\var}";  // "unexpected T_NS_SEPARATOR"

Ambiguity

Answer 2

Try this

<?php
namespace App\login; 

$p = 'login';
$test2 = '\App\\'.$p.'\\MyClass';

$test = new $test2;

Vrablik

namespace must be first line of file. Isn't it? – Uranie

This most certainly works, I use it like this: $class = '\\'.$vendor.'\\'.$application.'\\Router'; return new $class(); – Navigate

what is the rule of using single or double `\`s here ? – Credenza

@IstiaqueAhmed i don't think there's a rule here \A just happens to not be an escape character. its probably better to always escape the `` in this case either way – Remove

An explanation of the results would be very appreciated. – Pizor

Answer 3

No they cannot, as mario said.

To encapsulate variables use Classes. Polluting the global variable space should definitely be avoided.

• Example

  class_dbworker.php:

  class DbWorker
  {
      //properties and method logic
  }
  
  class DbWorkerData
  {
      public static $hugerelationsmap = array(....);
      public static ....
  }
  

  mainapp.php:

  include_once 'class_dbworker.php';
  print_r( DbWorkerData::$hugerelationsmap );
  

• Example using namespaces

  class_dbworker.php:

  namespace staticdata;
  class DbWorker
  {
      //properties and method logic
  }
  
  class DbWorkerData
  {
      public static $hugerelationsmap = array(....);
      public static ....
  }
  

  mainapp.php:

  include_once 'class_dbworker.php';
  
  use staticdata as data;
  
  print_r( \data\DbWorkerData::$hugerelationsmap );
  

Loewe

Answer 4

You can bound a variable to the namespace by wrapping the variable inside a function.

<?php
 namespace furniture;
// instead of declaring a $version global variable, wrap it inside a function
function version(){
 return "1.3.4";
}
?>

Manno

Answer 5

It is not possible because $MYVARNAME is still in the global scope. Try following code.

namespace.php

<?php
    namespace MYNAME;
    use MYNAME as M;
    const MYVAR   = 'MYVARNAME';

    ${M\MYVAR}    = date('Y');
    echo $MYVARNAME;  // PRINT YEAR
    $MYVARNAME    = 'X';
    echo $MYVARNAME;  // PRINT X
    echo ${M\MYVAR} ; // PRINT X

    include('file.php');
?>

file.php

<?php
    ${MYNAME\MYVAR}=date('Y');
    echo $MYVARNAME;        // PRINT YEAR
    $MYVARNAME = 'X';
    
    echo $MYVARNAME;        // PRINT X
    echo ${MYNAME\MYVAR};   // PRINT X
    
    include('file2.php');
?>

file2.php

<?php
    namespace MYNAME2;
    use MYNAME2 as N;
    const MYVAR   = 'MYVARNAME';

    ${N\MYVAR}    = 'Y';
    echo $MYVARNAME;  // PRINT Y
    echo ${MYNAME\MYVAR}; /* PRINT Fatal error: Uncaught Error:
    Undefined constant 'MYNAME2\MYNAME\MYVAR' */
?>

Aorangi

Answer 6

It can be done - sort of.

This is probably extremely bad and should never be done, but it is possible by using variable variables, and the magic constant for namespace. So a string-variable to name the variable we want to use, like so:

<?php
namespace your\namespace;

$varname = __NAMESPACE__.'\your_variablename'; //__NAMESPACE__ is a magic constant
$namespaced_variable = $$varname; //Note the double dollar, a variable variable
?>

Pickering

The question was Can PHP namespaces contain variables? not Can PHP variables contain namespaces? – Loewe

Answer 7

Store Complete classPath in Variable and use after 'new'.

It is very important to realize that because the backslash is used as an escape character within strings, it should always be doubled when used inside a string.

<?php
$a = "namespace\\className"; // 'which will print namespace/className'
$obj = new $a;
?>

Amphimixis

Answer 8

Alternate ways that can make code more organized:

Instead of like \view\header\$links:

(1) Backslashes in array key for imaginary nesting, Example:

$myVar['view\header\links'] = 'value';

// OR use multidimentional arrays

$view['header']['links'] = 'value';

(1.1) Use Global Array, Example

// START - SETUP

define('I', 'mySite_19582730');

// END - SETUP


// Usage:

$GLOBALS[I]['view\header\links'] = 'value';

// OR

$GLOBALS[I]['view__header__links'] = 'value';

(1.1.1) Functions to get & set value in Global Array

function set($key, $val){
    if (is_string($key)) $GLOBALS['site_8619403725'][$key] = $val;
    elseif (is_array($key)){
        foreach($key as $ky => &$vl) {
            $GLOBALS['mySite_19582730'][$vl] = $val;
        }
    }
}

function get($key){
    return @ $GLOBALS['mySite_19582730'][$key];
}

// Usage

set('view\header\search','<div></div>');
set(['view\header\logo','view\header\homeLink'], '<a href=""></a>');
get('view\header\search');

(2) Use __ (double underscores) in variable name to make imaginary nesting, Example:

$view__header__links = 'value';

Martainn