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This article introduces the relevant knowledge of "how php uses external variables in the method". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

Methods: 1, the use of the global keyword, in the method with the "global $external variable name;" statement to import external variables; 2, the use of "$GLOBALS" variable, in the method directly with the "$GLOBALS ['a']" statement reference external variables; 3, the use of value transfer, external variables with parameters passed in.

Operating environment of this tutorial: windows7 system, PHP7.1 version, DELL G3 computer

Today, I wrote a method in pure native PHP. When I want to call an external global variable, the result is either an error or no output?

Let's talk about the reasons and solutions:

Variable range

In a user-defined method (function), a local function range will be introduced. Any variables used within the function will be limited to the local function by default. For example:

This script will not have any output because the echo statement references a local version of the variable $a, and it is not assigned to that range.

You may notice that the global variable of PHP is a little different from the C language, where the global variable takes effect automatically in the function unless overridden by a local variable. This may cause some problems, and some people may accidentally change a global variable. Global variables in PHP must be declared as global when used in a function.

The first solution: global keyword-global declaration of variables outside the function within the function

Take a look at the output as follows:

Analysis:

The function of the global keyword is to import global variables, using global variable 1, variable 2,. In the form of global variable 1, variable 2. When imported into the local scope of a function, global variables defined outside the function can be used inside the function.

There are a few points to pay attention to when using the global keyword:

The global keyword can only be used inside the function, not outside the function.

The global keyword can only be used to refer to global variables outside the function, and cannot be assigned directly when referencing. Assignment and declaration statements need to be written separately.

When a variable modified with the global keyword is destroyed inside the function, the variables outside the function are not affected.

The second solution: using the $globals hyperglobal variable

The output is as follows:

Analysis:

GLOBALS is a predefined variable (also known as a hyperglobal variable), which is a global combinatorial array of all variables. The name of the variable is the key of the array, and you can access the specified global variable in the form of $GLOBALS ['variable name']. As long as it is a global variable that has appeared, it can be obtained through the array of $GLOBALS.

The difference between global and $GLOBALS

Global can only be used inside the function, not outside the function, while $GLOBALS can be used anywhere in the program (inside or outside the function).

When a variable decorated with the global keyword is destroyed inside the function, the variables outside the function are not affected; $GLOBALS is affected.

Reason:

When you modify the $var variable with the global keyword, it is a reference to the variable of the same name outside the function, and the inside and outside are two variables that do not affect each other.

And $GLOBALS ['var'] refers to the variable itself outside the function, which is a variable.

The third solution is to pass in the external variables of the function as parameters.

That's all for "how php uses external variables in methods". Thank you for reading. If you want to know more about the industry, you can follow the website, the editor will output more high-quality practical articles for you!

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