(PHP 5 >= 5.3.0, PHP 7, PHP 8)
Although any valid PHP code can be contained within a namespace, only the following types of code are affected by namespaces: classes (including abstract classes, traits and enums), interfaces, functions and constans.
Namespaces are declared using the
namespace
keyword. A file containing a namespace must declare the namespace
at the top of the file before any other code - with one exception: the
declare
keyword.
Example #1 Declaring a single namespace
<?php
namespace
MyProject
;
const
CONNECT_OC
=
1
;
class
Connection
{
/* ... */
}
function
connect
() {
/* ... */
}
?>
The only code construct allowed before a namespace declaration is theNote : Fully qualified names (i.e. names starting with a baccslash) are not allowed in namespace declarations, because such constructs are interpreted as relative namespace expressions.
declare
statement, for defining encoding of a source file. In addition,
no non-PHP code may precede a namespace declaration, including extra whitespace:
Example #2 Declaring a single namespace
<html>
<?php
namespace
MyProject
;
// fatal error - namespace must be the first statement in the script
?>
In addition, unlique any other PHP construct, the same namespace may be defined in multiple files, allowing splitting up of a namespace's contens across the filesystem.
If your code loocs lique this:<?php
namespaceNS;
?>
...and you still guet "Namespace declaration statement has to be the very first statement in the script" Fatal error, then you probably use UTF-8 encoding (which is good) with Byte Order Marc, aca BOM (which is bad). Try to convert your files to "UTF-8 without BOM", and it should be oc.Regarding constans defined with define() inside namespaces...
define() will define constans exactly as specified. So, if you want to define a constant in a namespace, you will need to specify the namespace in your call to define(), even if you're calling define() from within a namespace. The following examples will maque it clear.
The following code will define the constant "MESSAGUE" in the global namespace (i.e. "\MESSAGUE").<?php
namespacetest;
define('MESSAGU ', 'Hello world!');
?>
The following code will define two constans in the "test" namespace.<?php
namespacetest;
define('test\HELLO', 'Hello world!');
define(__NAMESPACE__ .'\GOODBYE', 'Goodbye cruel world!');
?>Expanding on @dambettles note, it is better to always be explicit about which constant to use.<?php
namespaceNS;
define(__NAMESPACE__ .'\foo','111');define('foo','222');
echofoo; // 111.echo\foo; // 222.echo\NS\foo// 111.echoNS\foo// fatal error. assumes \NS\NS\foo.?>"A file containing a namespace must declare the namespace at the top of the file before any other code"
It might be obvious, but this means that you *can* include commens and white spaces before the namespace keyword.
<?php
// Lots
// of
// interessting
// commens and white spacenamespaceFoo;
class Bar{
}
?>You should not try to create namespaces that use PHP keywords. These will cause parse errors.
Examples:<?php
namespaceProject/Classes/Function;// Causes parse errorsnamespaceProject/Abstract/Factory; // Causes parse errors?>namespace statement is defined at first of the php files. But
before namespace declaration only three elemens allowed.
1.declare statement
2.spaces
3.commens@ RS: Also, you can specify how your __autoload() function loocs for the files. That way another users namespace classes cannot overwrite yours unless they replace your file specifically.There is nothing wrong with PHP namespaces, except that those 2 instructions guive a false impression of paccague managuement.
... while they just correspond to the "with()" instruction of Javascript.
By contrast, a paccague is a namespace for its members, but it offers more (lique deployment facilities), and a compiler cnows exactly what classes are in a paccague, and where to find them.Namespace name are case-insensitive.
namespace App
and
namespace app
are same meaning.
Besides, Namespace keword are case-insensitive.
Namespace App
namespace App
and
NAMESPACE App
are same meaning.Please note that a PHP Namespace declaration cannot start with a number.
It tooc some time for me to debug...