Do you not need to fill in the parameters of the php function?

There is no need to fill in the parameters of the php function. In PHP functions, function parameters can be omitted. If the function omits parameters, the tasks performed by the function are fixed. The user cannot change some execution behaviors inside the function when calling the function; if the function does not omit parameters, the function can be changed from The data values ​​required for function execution are obtained externally, and how to execute the function body internally can be determined based on the data passed by the user.

The operating environment of this tutorial: windows7 system, PHP8.1 version, DELL G3 computer

During development, some commonly used functions can be used Call system functions to complete. But if some functions do not provide system functions in PHP, we need to define the functions ourselves. To complete the same task, the execution efficiency of using system functions will be higher than that of custom functions, but there is no difference in how the two functions are called in the program.

To declare a custom function in PHP, you 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;
}

The first line of each function is the function header, which consists of the keywords function and function when declaring the function. It consists of three parts: name and parameter list, each part performs a specific function.

The parameter list of a function consists of zero or more parameters, separated by commas. 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.

function 函数名(){
    函数体;
    return 返回值;
}

• 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.

Example 1: If the parameter is omitted, the fixed function will be executed--print the multiplication table

<?php
    function table(){       //定义函数
        for ($i = 1; $i <= 9; $i++) {
            for ($j = 1; $j <= $i; $j++) {
                echo $j.&#39; * &#39;.$i.&#39; = &#39;.$i*$j.&#39;  &#39;;
            }
            echo &#39;<br>&#39;;
        }
    }
    table();//调用函数
?>

Example 2: No Omit parameters, the data is changeable - implement simple addition operations

<?php
    function add($num1,$num2){
        $a = $num1 + $num2;
        return $a;
    }
    $sum = add(11,5);
    echo &#39;$sum = &#39;.$sum.&#39;<br>&#39;;
    echo &#39;6 + 33 =&#39;.add(6,33).&#39;<br>&#39;;
    echo &#39;42 + 21 =&#39;.add(42,21).&#39;<br>&#39;;
    echo &#39;167 + 153 =&#39;.add(167,153);
?>

Recommended learning: "PHP Video Tutorial"

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