How to use functions in php learning_PHP tutorial

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

Copy Code The code is as follows:

Function function_name($argument1,$argument2,$argument3,...$argumentn)
{
//Function Code code
Return return value;
}

In the above syntax structure, the meaning of the keywords is as follows.
(1) function: The key used to declare user-defined functions Word.
(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 Optionally, you can pass no 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, curly braces are not needed.
(5)Return: Return the value required by the calling code. Any type can be returned, including lists and objects. This results in The function immediately ends its execution and passes control back to the line on which it was called.
2, no-argument function
code func_1.php

Copy code The code is as follows:

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

3, there are parameter functions
PHP supports passing parameters by value (default), passing by reference and default parameter values. Variable length parameters Lists are only supported in PHP4 and subsequent versions.
(1) Value passing parameters. Parameter passing by value is the default passing method of PHP. Using this method, a value (parameter) must be passed when the main program is called.
Code sum.php

Copy code The code is as follows:

function sum ($ a,$b)
{
Echo $a+$b;
}
sum(100,20); //Start calling the function
?>

(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. Passing by reference is actually address passing, passing the address of a variable as a parameter.
Code valuechange.php

Copy code The code is as follows :

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

(3)Default value Parameters. 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,
class Member or function call.
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

Copy code The code is as follows:

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

http://www.bkjia.com/PHPjc/325657.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/325657.htmlTechArticle1. Declaring functions In PHP, the method of defining functions is almost the same as in other programming languages. The following is the PHP declaration function Syntax structure: Copy the code as follows: Function function_name($argument...