What are local variables? Detailed explanation of local variable examples in the scope of PHP variables

The scope of php variables

The scope of the variable is also its effective scope. Most PHP variables have a single scope of use, including files introduced by include and require. When a variable performs the assignment action, it will have different usage scopes depending on the difference in the declared regional location. The previous chapter introduced php variable functions and function reference and dereference. Generally speaking, variables are divided into local variables and global variables based on the position of declaration. In this chapter, we will first introduce local variables.

What local variable?

Local variables are also called internal variables. They are variables declared inside a function. Their scope is limited to the inside of the function. It is illegal to use this variable after leaving the function. An error will occur during program execution. Information. Not only the variables declared in the function are local variables, but the parameters set for declaring the function are also local variables because they can only be used inside this function. The difference is that the specific values ​​of the parameters of the function are obtained from outside the function (the value is passed in when the function is called), while variables declared directly in the function can only be assigned values ​​inside the function. But their scope is limited to the inside of the function, because the variables inside the function will be declared every time the function is called, and the variables inside the function will be released after execution.

The following is a code example to demonstrate:

<?php
  /*
  * 测试局部变量的演示函数
  * $one 需要一个整型的参数，测试是否为局部变量
  */
  function num($one){
    // 在函数内部声明变量
    $two = 2;
    // 在函数内部使用两个全局变量
    echo "函数内部：$one + $two = ".($one+$two).&#39;<br>&#39; ;
  }
  // 调用 num 函数并赋值给参数
  num(6);
  // 在函数外部使用两个变量，为非法访问
  echo "函数外部：$one + $two = ".($one+$two);
?>

The above program will output the following results after execution :

函数内部：6 + 2 = 8          //在函数内部可以访问内部变量，输出结果
函数外部： + = 0            // 在函数外部不能访问函数内部的两个变量，所以无法输出结果

In the above example, a num() function is declared. When the num() function is called, two variables $one and $twe are declared. Both variables are local variables. The variable $one is declared in the parameter and assigned when called. The other variable $two is declared in the function and assigned directly. These two local variables can only be used inside the function and output the calculated results. When the num() function ends, these two variables will be released. Therefore, these two box variables do not exist when accessed outside the function, so there is no output result. If the variable value needs to be called outside the function, its value must be transferred back to the main program block through the return instruction for subsequent processing.

The code is as follows:

<?php
  /*
  * 测试局部变量的演示函数
  * $one 需要一个整型的参数，测试是否为局部变量
  */
  function num($one){
    // 在函数内部声明变量
    $two = 2;
    // 将函数的运算结果使用 return 语句返回到函数调用处
    return $one + $two;
  }
  // 调用 num 函数并赋值给参数 $one，返回值付给变量 $sum
  $sum = num(6);
  // 在函数外部可以使用函数返回的结果
  echo "函数外部使用：$sum";
?>

After the above program is executed, the following results will be output:

函数外部使用：8                 //获得函数内部执行结果，在函数外部使用。

The above is the scope of the php variable Examples of local variables are introduced. The next chapter will introduce the global variables in the php scope. Friends, please continue to pay attention to the following content.

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