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Today, I will talk to you about the analysis of the scope of variables in PHP. Many people may not know much about it. In order to make you understand better, the editor has summarized the following content for you. I hope you can get something according to this article.

The variable scope in the PHP interview is a common and compulsory question in the interview. Here are some points to pay attention to in the interview:

# living example one

$A = "Hello"

Functionprint_A ()

{

A = "phpmysql!!"

Global $A

/ / the global global variable function is defined externally by an independent module $A.

Echo $A

}

Echo $A; / / output Hello

Print_A (); / / out pot Hello

When you define $An as a global variable, you do not change the value of $A

Test venue:

The scope of local variables and global variables, the external variables of the function are global variables (this page and the introduction page), and the internal variables of the function are local variables.

Easy to make mistakes:

The interviewer can not distinguish the concept of local variable from global variable, so that the output result of the function can not be written accurately.

Analysis:

1) Local variables can only be used within the function and will be invalidated no matter how they are modified externally, which ensures that we are on the same page.

No exception occurs when you define a variable with the same name

2) globally, it can be declared when multiple functions and multiple pages are needed, which can save memory space, but the definition is overwritten repeatedly during application.

Attention should also be paid to the problems caused by the cover.

# living example two

Function test () {

$num = 10

Echo $num

}

Test (); / / output 10

Echo $num

$num = $num+10

Echo $num

Analysis:

The above code will result in a waring with an undefined variable, which we will ignore

1) $num is a local variable, so you output inside the function and output 10 when you call the function method, but no matter what you do outside

The variable $num is not the same variable, so it will not have a substantial effect.

After reading the above, do you have any further understanding of the problem resolution of variable scope in PHP? If you want to know more knowledge or related content, please follow the industry information channel, thank you for your support.

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