笨鳥(niǎo)學(xué)php(5) 函數(shù)的聲明與使用
Jun 13, 2016 pm 12:03 PM
笨鳥(niǎo)學(xué)php(五) 函數(shù)的聲明與使用
1、函數(shù)的聲明
<?php /** * function 函數(shù)名(參數(shù)1, 參數(shù)2.... ){ * 函數(shù)體; * 返回值; * } */ $sum = sum(3, 4); echo $sum; function sum($x, $y){ $sum = 0; $sum = $x * $x + $y + $y; return $sum; }?>
2、變量的范圍
局部變量: 在函數(shù)中聲明的變量就是局部變量, 只能在自己的函數(shù)內(nèi)部使用。
全局變量: 在函數(shù)外聲明的變量就是全局變量, 在變量聲明以后直到整個(gè)腳本結(jié)束前都可以使用, 包括在函數(shù)中和 { } 中都可使用。
2.1 知識(shí)點(diǎn): PHP的變量分不出是聲明還是使用
<?php $a = 10; function demo($a){ $a += 10; echo $a . '<br>'; } demo($a); echo $a; // 結(jié)果: 20, 10 // PHP的變量分不出 $a 是聲明還是使用?>2.2 知識(shí)點(diǎn): 函數(shù)中使用全局變量必須使用global關(guān)鍵字, 在聲明global之后的變量才是全局的變量
<?php $a = 10; function demo() { global $a; $a += 10; echo $a . " demo <br>"; } function test() { global $a; $a += 5; echo $a . "test <br>"; } echo $a . " ----<br>"; // 10 ---- demo(); // 20 demo echo $a . " !!!!<br>"; // 20 !!!! demo(); // 30 demo echo $a . " @@@@<br>"; // 30 @@@@ test(); // 35 test echo $a . " ####<br>"; // 35 ####?>
靜態(tài)變量: 只能聲明在函數(shù)中(類中), 不能在全局聲明, 變量前使用static關(guān)鍵字修飾。
2.3 知識(shí)點(diǎn): 靜態(tài)變量在靜態(tài)代碼塊中存儲(chǔ), 它的值可以一個(gè)函數(shù)多次調(diào)用之間共享, 但只在第一次調(diào)用函數(shù)時(shí)聲明到內(nèi)存
以后再調(diào)用時(shí)就不再聲明而直接使用(和Java類似)。
<?php function test(){ static $a = 0; $a++; echo $a."<br>"; } test(); // 1 test(); // 2 test(); // 3?>
3、變量函數(shù)
其實(shí)這個(gè)和JS又很類似, 例如: 定義$var = hello, 下次使用$var()時(shí)就將尋找與變量值同名的函數(shù)hello()
<?php function one($a, $b){ return $a + $b; } function two($a, $b){ return $a * $a + $b * $b; } function three($a, $b){ return $a * $a * $a + $b * $b * $b; } //$var = one; //$var = "two"; $var = three; echo "結(jié)果:".$var(3, 4)."<br>"; // 91?>
4、系統(tǒng)函數(shù)
4.1 常規(guī)函數(shù) ????? bool copy (string source, string dest)
4.2 帶有mixed, mixed表示可以傳任何類型的數(shù)據(jù)
????? bool chown (string filename, mixed user)
????? ?
4.3 帶有&參數(shù)的函數(shù), 表示引用賦值, 這個(gè)參數(shù)不能傳值, 只能傳一個(gè)變量,然后函數(shù)將變量的值改變,
????? 我們?cè)谑褂眠@個(gè)變量時(shí),值也是變化的(和Java中傳引用又是一樣的)
?? ?? bool arsort (array &array [, int sort_flags])<?php $arr=array(1, 9, 5, 8, 3, 4); sort($arr); print_r($arr);?>4.4 默認(rèn)函數(shù), 帶有[]的函數(shù), 表示這個(gè)參數(shù)是可選的,如果你傳值了就使用你傳的值,如果沒(méi)有傳值則使用默認(rèn)值
?? ? bool arsort (array &array [, int sort_flags])
<?php function demo($a=1, $b=20, $c){ echo "### $a ### $b ### $c ###<br>"; } demo(8,9);?>4.5 帶有...的參數(shù)函數(shù), ...表示可以傳任意多個(gè)參數(shù)
????? int array_unshift (array &array, mixed var [, mixed ...])
<?php function demo(){ $sum = 0; for($i = 0; $i < func_num_args(); $i++){ $sum += func_get_arg($i); } return $sum; } echo demo(1, 2, 3, 4, 5, 6, 7, 8, 9);?>
4.6 回調(diào)函數(shù) 帶有callback,? 就是調(diào)用這個(gè)函數(shù)時(shí)需要我們傳一個(gè)函數(shù)進(jìn)來(lái)(函數(shù)名,函數(shù)名字串)
????? array array_filter (array input [, callback callback])
<?php function demo($n){ if($n % 2== 0){ return true; }else{ return false; } } $a = array(1, 2, -3, 4, -5, 6, -7, 8, 9); print_r(array_filter($a, demo)); // Array ( [1] => 2 [3] => 4 [5] => 6 [7] => 8 ) ?>

Hot AI Tools

Undress AI Tool
Undress images for free

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

Notepad++7.3.1
Easy-to-use and free code editor

SublimeText3 Chinese version
Chinese version, very easy to use

Zend Studio 13.0.1
Powerful PHP integrated development environment

Dreamweaver CS6
Visual web development tools

SublimeText3 Mac version
God-level code editing software (SublimeText3)

Hot Topics

The message "Your organization has asked you to change your PIN" will appear on the login screen. This happens when the PIN expiration limit is reached on a computer using organization-based account settings, where they have control over personal devices. However, if you set up Windows using a personal account, the error message should ideally not appear. Although this is not always the case. Most users who encounter errors report using their personal accounts. Why does my organization ask me to change my PIN on Windows 11? It's possible that your account is associated with an organization, and your primary approach should be to verify this. Contacting your domain administrator can help! Additionally, misconfigured local policy settings or incorrect registry keys can cause errors. Right now

Windows 11 brings fresh and elegant design to the forefront; the modern interface allows you to personalize and change the finest details, such as window borders. In this guide, we'll discuss step-by-step instructions to help you create an environment that reflects your style in the Windows operating system. How to change window border settings? Press + to open the Settings app. WindowsI go to Personalization and click Color Settings. Color Change Window Borders Settings Window 11" Width="643" Height="500" > Find the Show accent color on title bar and window borders option, and toggle the switch next to it. To display accent colors on the Start menu and taskbar To display the theme color on the Start menu and taskbar, turn on Show theme on the Start menu and taskbar

By default, the title bar color on Windows 11 depends on the dark/light theme you choose. However, you can change it to any color you want. In this guide, we'll discuss step-by-step instructions for three ways to change it and personalize your desktop experience to make it visually appealing. Is it possible to change the title bar color of active and inactive windows? Yes, you can change the title bar color of active windows using the Settings app, or you can change the title bar color of inactive windows using Registry Editor. To learn these steps, go to the next section. How to change title bar color in Windows 11? 1. Using the Settings app press + to open the settings window. WindowsI go to "Personalization" and then

Taskbar thumbnails can be fun, but they can also be distracting or annoying. Considering how often you hover over this area, you may have inadvertently closed important windows a few times. Another disadvantage is that it uses more system resources, so if you've been looking for a way to be more resource efficient, we'll show you how to disable it. However, if your hardware specs can handle it and you like the preview, you can enable it. How to enable taskbar thumbnail preview in Windows 11? 1. Using the Settings app tap the key and click Settings. Windows click System and select About. Click Advanced system settings. Navigate to the Advanced tab and select Settings under Performance. Select "Visual Effects"

Do you see "A problem occurred" along with the "OOBELANGUAGE" statement on the Windows Installer page? The installation of Windows sometimes stops due to such errors. OOBE means out-of-the-box experience. As the error message indicates, this is an issue related to OOBE language selection. There is nothing to worry about, you can solve this problem with nifty registry editing from the OOBE screen itself. Quick Fix – 1. Click the “Retry” button at the bottom of the OOBE app. This will continue the process without further hiccups. 2. Use the power button to force shut down the system. After the system restarts, OOBE should continue. 3. Disconnect the system from the Internet. Complete all aspects of OOBE in offline mode

Screen brightness is an integral part of using modern computing devices, especially when you look at the screen for long periods of time. It helps you reduce eye strain, improve legibility, and view content easily and efficiently. However, depending on your settings, it can sometimes be difficult to manage brightness, especially on Windows 11 with the new UI changes. If you're having trouble adjusting brightness, here are all the ways to manage brightness on Windows 11. How to Change Brightness on Windows 11 [10 Ways Explained] Single monitor users can use the following methods to adjust brightness on Windows 11. This includes desktop systems using a single monitor as well as laptops. let's start. Method 1: Use the Action Center The Action Center is accessible

We all have different preferences when it comes to display scaling on Windows 11. Some people like big icons, some like small icons. However, we all agree that having the right scaling is important. Poor font scaling or over-scaling of images can be a real productivity killer when working, so you need to know how to customize it to get the most out of your system's capabilities. Advantages of Custom Zoom: This is a useful feature for people who have difficulty reading text on the screen. It helps you see more on the screen at one time. You can create custom extension profiles that apply only to certain monitors and applications. Can help improve the performance of low-end hardware. It gives you more control over what's on your screen. How to use Windows 11

The activation process on Windows sometimes takes a sudden turn to display an error message containing this error code 0xc004f069. Although the activation process is online, some older systems running Windows Server may experience this issue. Go through these initial checks, and if they don't help you activate your system, jump to the main solution to resolve the issue. Workaround – close the error message and activation window. Then restart the computer. Retry the Windows activation process from scratch again. Fix 1 – Activate from Terminal Activate Windows Server Edition system from cmd terminal. Stage – 1 Check Windows Server Version You have to check which type of W you are using
