A detailed introduction to PHP variables

What is a global variable? A global variable, also known as an external variable, is defined outside the function and is scoped to the end of the program file, starting at the definition of the variable. Unlike other programming languages, global variables are not automatically set to be available. In the previous section we introduced the local variables of the scope of the PHP variable, in PHP, because the function can be treated as a separate program snippet, so the local variable overrides the visibility of the global variable, so the global variable cannot be called directly in the function. The format of its code is as follows: <?php $one = 10; $two = 20; The test cannot use global variables directly inside the function $one and $two function sum () {//Two variables that are newly declared inside the function and do not have an initial value assigned

1. What are global variables? Examples of global variables for the range of PHP variables

Summary: A global variable, also known as an external variable, is defined outside the function and is scoped to the end of the program file, starting at the definition of the variable.

2. What is a local variable? Example of a local variable in the scope of a PHP variable

Summary: The scope of a variable is also its scope of entry. Most PHP variables have only a single scope of use, and also include the files introduced by include and require.

3. PHP variable function and function reference and dereference instance detailed

Introduction: In PHP is to support variable functions, first define some functions, then declare a variable, use variables to invoke different functions, and then constantly re-assign values. Below we will introduce a concrete example of how variable functions are used.

4. Assignment of PHP variables: The difference between value passing and reference passing

Introduction: A variable refers to the amount of value that can be changed during the execution of the program, it is used to save a value, it is convenient for us to call, but there are two ways in which PHP assigns variables: value passing and reference passing, these two methods of assigning values to variables are different, this chapter, Let's take a look: the difference between value passing and reference passing

5. PHP variable Scope instance detailed

Summary: Variables are used, to conform to the definition rules for variables. Variables have to be used in a valid range, and if the variable goes beyond a finite range, the variable is meaningless, as if we had 100 dollars, we can buy 100 dollars or less, if the item exceeds 100 yuan, then these 100 pieces will not be used. 100 dollars is the equivalent of this variable, and the range within 100 blocks is equivalent to the scope.

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