Several points to note when defining command space in PHP-PHP Tutorial-php.cn

Several points to note when defining command space in PHP

墨辰丷

Release： 2023-03-28 15:26:02

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This article mainly introduces several points to pay attention to when defining command space in PHP. Interested friends can refer to it. I hope it will be helpful to everyone.

1. Declaring the command space must be the first statement of the program script. In addition, all non-PHP code, including whitespace, cannot appear before the namespace declaration.

The following is an example of an error:

<html>
<?php
namespace MyProject; // 致命错误 -　命名空间必须是程序脚本的第一条语句
?>

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This is also wrong

<?php 
// Lots 
// of 
// interesting 
// comments and white space 

namespace Foo; 
class Bar { 
} 
?>

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2. PHP keywords cannot be used.

The following is an error example:

<?php 
namespace Project/Classes/Function; // Causes parse errors 
namespace Project/Abstract/Factory; // Causes parse errors 
?>

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3. Constant definition in the namespace .

The following MESSAGE is in the global namespace:

<?php
namespace test;
define(&#39;MESSAGE&#39;, &#39;Hello world!&#39;);
?>

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Define 2 constants in the test namespace:

<?php
namespace test;
define(&#39;test\HELLO&#39;, &#39;Hello world!&#39;);
define(__NAMESPACE__ . &#39;\GOODBYE&#39;, &#39;Goodbye cruel world!&#39;);
?>

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The above is the entire content of this article, I hope it will be helpful to everyone's study.

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