php namespace (detailed answer combined with code)

In php## namespace, you need to know the terminology of the three names of spaces: unqualified names, qualified names, fully qualified names, and how PHP parses them. The official documents are very good, so I just used them. Understanding them is very helpful for learning the following content. We learned earlier about the subspace and public space of the namespace. It makes sense that the calling syntax of the namespace is like a file path. It allows us to customize the subspace to describe the relationship between each space.

The terms for the three names in the namespace are as follows:

1. Unqualified name, or class name that does not include a prefix, such as $comment = new Comment();. If the current namespace is Blog\Article, Comment will be parsed as Blog\Article\Comment. If the code using Comment does not contain code in any namespace (in the global space), the Comment will be parsed as a Comment.

2. Qualified name, or name containing prefix, such as $comment = new Article\Comment();. If the current namespace is Blog, Comment will be parsed as Blog\Article\Comment. If the code using Comment does not contain code in any namespace (in the global space), the Comment will be parsed as a Comment.

3. Fully qualified name, or a name that includes the global prefix

operator, such as $comment = new \Article\Comment();. In this case, Comment is always resolved to the literal name Article\Comment in the code.

In fact, these three names can be compared to file names (such as comment.php), relative path names (such as ./article/comment.php), and absolute path names (such as /blog/article/comment. php) which might be easier to understand.

Create a Blog space here, using an unqualified name to represent the current Blog space. This call will be parsed after instantiation. Use a qualified name to indicate that it is relative to the Blog space. After instantiation, this call will be parsed into Blog\Article\Comment(). Note that there is no backslash in front of the class. Use a fully qualified name, indicating that it is absolute to the Blog space. This call will be parsed after instantiation. Note the difference between a backslash in front of the class and no backslash.

The sample code is as follows:

[html] view plain copy
<?php  
//创建空间Blog  
namespace Blog;  
class Comment { }  
//非限定名称，表示当前Blog空间  
//这个调用将被解析成 Blog\Comment();  
$blog_comment = new Comment();  
//限定名称，表示相对于Blog空间  
//这个调用将被解析成 Blog\Article\Comment();  
$article_comment = new Article\Comment(); //类前面没有反斜杆\  
//完全限定名称，表示绝对于Blog空间  
//这个调用将被解析成 Blog\Comment();  
$article_comment = new \Blog\Comment(); //类前面有反斜杆\  
//完全限定名称，表示绝对于Blog空间  
//这个调用将被解析成 Blog\Article\Comment();  
$article_comment = new \Blog\Article\Comment(); //类前面有反斜杆\  
//创建Blog的子空间Article  
namespace Blog\Article;  
class Comment { }  
?>

The above is the php namespace I compiled for everyone. I hope it will be helpful to everyone in the future.

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