What do php parameters mean?

In PHP, parameters are the ports for data exchange inside and outside the function. The input of data in the function is completed by parameters. According to the position where the parameters are used, parameters are divided into formal parameters and actual parameters: 1. Formal parameters are the parameter list in parentheses after the function name when defining the function. The formal parameters themselves have no specific values; 2. Actual parameters are the parameters when the user calls the function. A function is a number of parameters in parentheses after the function name. The actual parameters and formal parameters need to correspond one-to-one in order. It will replace the corresponding variable values ​​of the formal parameters in the function body.

The operating environment of this tutorial: windows7 system, PHP version 8.1, DELL G3 computer

Declaring a custom function in PHP can Use the following syntax format:

function 函数名 (参数1, 参数2, ..., 参数n){
    函数体;
    return 返回值;
}

• When declaring a function, the parentheses "()" after the function name are also required. The parentheses contain a set of acceptable parameter lists. , the parameters are declared variables, and then the variables can be passed to the function when calling the function. The parameter list can be empty, or it can have one or more parameters. Use commas to separate multiple parameters;

In PHP, just use the function name where you need to use the function. Make a function call with the parameter list:

函数名 (参数1, 参数2, ..., 参数n);

It can be seen that: The parameter list of the function is composed of zero or more parameters, separated by commas between each parameter. So what are parameters?

Parameters are the ports for data exchange inside and outside the function. The input of data in the function is completed by parameters.

If the function does not have a parameter list, the task performed by the function is fixed, and the user cannot change some execution behaviors inside the function when calling the function.

If the function has a parameter list, the function can obtain the data values ​​required for function execution from the outside. That is, when the user calls a function, before the function body is executed, some data is passed into the function through the parameter list of the function. In this way, when the function executes the function body, it can determine what is going on inside the function body based on the data passed by the user. implement.

According to the location where the parameters are used, parameters are divided into two types: formal parameters and actual parameters.

1. Formal parameters

Formal parameters are the parameter list in parentheses after the function name when defining a function (referred to as "formal parameters"), just like it The name is the same, the formal parameter itself has no specific value. Because the function body needs to use external parameters, in order for the parameters to be passed in correctly, it needs to be passed through the formal parameters and the data in the function body. The formal parameters are as shown in the figure below.

[Example] The formal parameters of a function are as follows:

<?php
    function hello($str){
        echo &#39;参数 $str 的值为：&#39;.$str.&#39;<br>&#39;;
    }
?>

Among them, the variable $str in parentheses after the function name in line 2 of the code is The formal parameters of this function.

2. Actual parameters

The actual parameters are the several parameters in parentheses after the function name when we call the function (referred to as "actual parameters"). The actual parameters and The formal parameters need to correspond one-to-one in order. It will replace the variable value corresponding to the formal parameter in the function body. The parameter of the function can be a specific value or a variable. The actual parameters are as shown in the figure below.

[Example] The following code demonstrates the actual parameters used when calling the function:

<?php
    function add($a, $b){
        echo $a.&#39; + &#39;.$b.&#39; = &#39;.($a+$b).&#39;<br>&#39;;
    }
    add(11, 32);
?>

Among them, the function name in line 6 of the code is in parentheses. 11 and 32 are the actual parameters.

Note: The actual parameters must be the same as the number of formal parameters, and correspond one to one, otherwise the program will go wrong.

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