How to use function in php_PHP tutorial-PHP Tutorial-php.cn

In the programming languages I know, the function command is used to define functions. Let’s introduce the usage of function in php.

User-defined functions are also called custom functions. They are not provided by PHP and are created by programmers. Since you create such functions yourself, you can fully control these functions. Therefore, you can make a function completely according to your own needs. Runs the way you want.

1, declare function

In PHP, the method of defining functions is almost the same as in other programming languages. The following is the syntax structure of PHP function declaration:

The code is as follows

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代码如下

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Function function_name($argument1,$argument2,$argument3,......$argumentn)

{

//函数代码code

Return 返回值;

}

Function function_name($argument1,$argument2,$argument3,...$argumentn)

{

//Function code code

Return return value;

}

In the above grammatical structure, the meaning of the keywords is as follows.

(1)function: keyword used to declare user-defined functions.

(2)function_name: The name of the function to be created. This name will be used when it is called later. The function name should be unique because PHP does not support overloading. When naming functions, you need to follow the variable naming

The same principle. But the function name cannot start with $, but the variable can.

(3)argument: The value to be passed to the function. The function can have multiple parameters, with commas between them. But the parameter items are optional, and you can not pass any parameters when calling the function.

(4)code: It is a piece of code that is executed when the function is called. If there are two or more statements, the code must be enclosed in curly brackets "{}". However, if there is only one code, then No need for braces.

代码如下

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require 'a.php';
echo "我不会被执行!";

(5)Return: Return the value required by the calling code. Any type can be returned, including lists and objects. This causes the function to immediately end its running and transfer control back to the line where it was called.

2, parameterless function

Code func_1.php

The code is as follows

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require 'a.php';
echo "I will not be executed!";

代码如下	复制代码
function sum ($a,$b) { Echo $a+$b; } sum(100,20); //开始调用该函数 ?>

?> 3, function with parameters PHP supports passing parameters by value (default), passing by reference and default parameter values. Variable length parameter lists are only supported in PHP4 and subsequent versions. (1) Pass parameters by value. Passing parameters by value is the default transfer method of PHP. Using this method, a value (parameter) must be passed when the main program is called. Code sum.php

(2) Reference parameters. When passing by value, only a copy of the parameters is passed to the called function. However, any modification to these values within the called function will not affect the calling function

The original value in . Passing by reference is actually address passing, passing the address of a variable as a parameter.

Code valuechange.php

Class members or function calls.

The code is as follows

代码如下

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$myNum=100;
function Valuechange ($number)
{
$number=$number+1;
Echo $number . "
";
       }
       Valuechange($myNum);
       Echo $myNum;
    ?>

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          $myNum=100;
         function Valuechange ($number)
              {
            $number=$number+1;
Echo $number . "
";
}
Valuechange($myNum);
Echo $myNum;
?>

(3) Default value parameter. Using the default parameter value passing method, the function must have a parameter when called. If there is no value used, the default value is passed to the function parameter. The default value must be a constant expression , not a variable,

代码如下	复制代码
$myNum=100; function Valuechange ($number) { $number=$number+1; Echo $number . " "; } Valuechange($myNum); Echo $myNum; ?>

Tip: When using default parameters, any default parameters must be placed to the right of the non-default parameters; otherwise, the function may not work as expected.

Code func_default.php

true

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TechArticleIn the programming languages I know, the function command is used to define functions. Let’s introduce it below. About the usage of functions in php. User-defined functions are also called custom...

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