How to define a function in php

A function is a collection of codes that completes a specific function and can be divided into system functions and user functions. Users can create custom functions to achieve specific needs.

1. Function definition syntax structure:

PHP allows users to create a custom function using the function keyword. Syntax structure:

function 函数名称(参数1, 参数2, ...)
{
//函数内的代码
}

PHP has fewer restrictions on function names. It can be any string starting with a letter or underscore followed by letters, underscores or numbers, and is not case-sensitive. Inside the parentheses are the parameters of the function. Multiple parameters are separated by commas. The parentheses cannot be omitted when there are no parameters. Within the curly braces is the function body. Use the return statement within the function body to specify the return value of the function. Example:

function format_Html($text){
$text="<u><i><b>$text</b></i></u>"; //应用加粗、斜体和粗体标记
echo $text; //输出格式化后的字符串
}

2. Using functions:

After the user function is created, it can be used like a system function, that is, called by specifying the function name. If the function requires parameters, the value of the parameter needs to be specified in parentheses. Note that the type of the parameter should be consistent with the definition.

When calling a user-defined function, you must ensure that the previous function already exists, that is, the function should be defined first and then called. Example:

<table cellspacing=0 cellpadding=0 width="511" border=0>
  <tr>
<td width="70" height=22>产品名称：</td>
<td width="292" height=22 class="title"><?php format_Html(“企业管理系统”); ?></td>
  </tr>
</table>

3. Function return value:

Sometimes you need to use the result of function execution outside the program. In this case, you need to use the return statement within the function to specify a return value. Use the return statement to return any type of data to a function. Example:

<?php
function getDataAry(){
$resAry=array(95,87,79,80,62,74,90,92); //创建一个数组
return $resAry; //返回该数组
}
$ary=getDataAry(); //保存函数返回的数组
foreach ($ary as $i) echo $i.","; //遍历数组，输出所有数
?>

4. Function parameter passing method:

The parameter passing methods supported by PHP are: passing by value, passing by index, passing by default value and passing by variable parameter list.

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