PHP第三课 PHP的基本数据类型
PHP第三课 PHP的基本数据类型
学习纲要:
1.php七种变量类型
2.isset和empty两个函数的区分3.类型测试
4.类型的自动转换
5.类型强制转换
注意:
1.对象中调用方法是通过 变量->方法名 来调用. $user1 = new per(); $user1->say();
2.更改页面的编码:
header ("content-type:text/html;charset=gbk");
3.header头信息不能有输出
1.php八种变量类型
整型
浮点型
字符型
布尔型
//以上四种类型是标量类型
数组
对象
//以上两种类型是复合类型
资源
null类型
//以上两种类型是特殊类型
整型
$a=10;
浮点型
$a=10.3;
字符型
$a="Hello World";
字符串链接用.来链接
<?php $hello = "Hello"; echo $hello." World"; ?>
布尔型
$a=true;
布尔类型一般都是由比较运算得到, > < >= <= == != === !==
用echo print_r输出一个布尔类型时,true会变成1,false会变成空
$a=true;
var_dump($a);
数组
//定义:给一个变量赋多个值的时候
<?php $arr=array("hello","world","junzaivip",88,true); echo "<pre class="code">"; print_r ($arr); echo "
数组的取值:
<?php $arr=array("hello","world","junzaivip",88,true); echo $arr[1]; ?>
数组的添加:
<?php $arr=array("hello","world","junzaivip",88,true); $arr[] = "d"; print_r($arr); ?>
对象类型
//对象由两部分组成:特征和功能,属性和方法
<?php header ("content-type:text/html;charset=gbk"); class per{ function say(){ echo "我正在说话"; } function eat(){ echo "我正在吃饭"; } function sleep(){ echo "我正在睡觉"; } function run(){ echo "我正在走路"; } } $user1 = new per(); $user1->say(); ?>
资源
null类型
$a=null;
基于数据库链接资源,操作表:
<?php //header("content-type:text/html;charset=utf-8"); $conn=mysql_connect("localhost","root","1234"); mysql_select_db("test");//选择数据库 mysql_query("set names utf8");//设置数据库编码为utf8 $sql="select * from user";//sql语句 //执行sql语句 $rst=mysql_query($sql); //拿出数据 while($row=mysql_fetch_assoc($rst)){ echo "<h1 id="ID-row-id"> ID:{$row['id']}</h1>"; echo "<h1 id="NAME-row-name"> NAME:{$row['name']}</h1>"; } ?>
2.isset和empty两个函数的区分
isset变量是否存在,不存在的情况:
1)没有定义
2)null
empty 变量是否为空,为空的情况:
1)0
2)""
3)"0"
4)false
5)array()
6)null
7)没有定义
3.类型测试
var_dump();
1.整型 is_int();
2.浮点型 is_float();
数据库连接: $conn = mysql_connect("localhost","root","1234");
var_dump(is_resource($conn));
?>
4.类型的自动转换
1.整型->字符串
<?php $num=1243; echo $num."abd"; ?>
2.字符串->整型
$num="1243alj";
//字符串自动转为整型
echo $num+1;
3.其他类型->布尔类型
1)0
2)""
3)"0"
4)false
5)array()
6)null
7)没有定义
//以上转布尔类型全是假的
5.类型强制转换
(int)$num 整型
(float)$num 浮点型
(String)$num 字符串
(bool)$num 布尔
删除变量使用:
$num="user";
unset($num);
var_dump(isset($num));
字符串的单双引号:
1.字符串中没有变量,就用单引号
2.如果有变量就用双引号(单引号也可以使用,但是需要用.来链接)
<?php // $str='Hello'; // $str2='World'; // echo $str.$str2; $name='小磊顺'; echo "我是{$name},我想睡一会"; echo '我是'.$name.',我想睡一会'; echo "我是".$name.",我想睡一会"; //字符串中没有变量,就用单引号,如果有变量就用双引号(单引号也可以使用,但是需要用.来链接) ?>
常量的定义:
//跟变量一样,但是一旦被定义就不能被修改
define("HOST","localhost");
define("USER","root");
define("PASS","123");
define("DBNAME","test");
//比如数据库的配置文件,这个时候要用常量,而且后面不能被修改.
常量的输出:
echo HOST;
常量不能放在双引号中
echo "my host is".HOST;
运算符

Hot AI Tools

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

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

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

AI Hentai Generator
Generate AI Hentai for free.

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

DDREASE is a tool for recovering data from file or block devices such as hard drives, SSDs, RAM disks, CDs, DVDs and USB storage devices. It copies data from one block device to another, leaving corrupted data blocks behind and moving only good data blocks. ddreasue is a powerful recovery tool that is fully automated as it does not require any interference during recovery operations. Additionally, thanks to the ddasue map file, it can be stopped and resumed at any time. Other key features of DDREASE are as follows: It does not overwrite recovered data but fills the gaps in case of iterative recovery. However, it can be truncated if the tool is instructed to do so explicitly. Recover data from multiple files or blocks to a single

0.What does this article do? We propose DepthFM: a versatile and fast state-of-the-art generative monocular depth estimation model. In addition to traditional depth estimation tasks, DepthFM also demonstrates state-of-the-art capabilities in downstream tasks such as depth inpainting. DepthFM is efficient and can synthesize depth maps within a few inference steps. Let’s read about this work together ~ 1. Paper information title: DepthFM: FastMonocularDepthEstimationwithFlowMatching Author: MingGui, JohannesS.Fischer, UlrichPrestel, PingchuanMa, Dmytr

The performance of JAX, promoted by Google, has surpassed that of Pytorch and TensorFlow in recent benchmark tests, ranking first in 7 indicators. And the test was not done on the TPU with the best JAX performance. Although among developers, Pytorch is still more popular than Tensorflow. But in the future, perhaps more large models will be trained and run based on the JAX platform. Models Recently, the Keras team benchmarked three backends (TensorFlow, JAX, PyTorch) with the native PyTorch implementation and Keras2 with TensorFlow. First, they select a set of mainstream

I cry to death. The world is madly building big models. The data on the Internet is not enough. It is not enough at all. The training model looks like "The Hunger Games", and AI researchers around the world are worrying about how to feed these data voracious eaters. This problem is particularly prominent in multi-modal tasks. At a time when nothing could be done, a start-up team from the Department of Renmin University of China used its own new model to become the first in China to make "model-generated data feed itself" a reality. Moreover, it is a two-pronged approach on the understanding side and the generation side. Both sides can generate high-quality, multi-modal new data and provide data feedback to the model itself. What is a model? Awaker 1.0, a large multi-modal model that just appeared on the Zhongguancun Forum. Who is the team? Sophon engine. Founded by Gao Yizhao, a doctoral student at Renmin University’s Hillhouse School of Artificial Intelligence.

Facing lag, slow mobile data connection on iPhone? Typically, the strength of cellular internet on your phone depends on several factors such as region, cellular network type, roaming type, etc. There are some things you can do to get a faster, more reliable cellular Internet connection. Fix 1 – Force Restart iPhone Sometimes, force restarting your device just resets a lot of things, including the cellular connection. Step 1 – Just press the volume up key once and release. Next, press the Volume Down key and release it again. Step 2 – The next part of the process is to hold the button on the right side. Let the iPhone finish restarting. Enable cellular data and check network speed. Check again Fix 2 – Change data mode While 5G offers better network speeds, it works better when the signal is weaker

Recently, the military circle has been overwhelmed by the news: US military fighter jets can now complete fully automatic air combat using AI. Yes, just recently, the US military’s AI fighter jet was made public for the first time and the mystery was unveiled. The full name of this fighter is the Variable Stability Simulator Test Aircraft (VISTA). It was personally flown by the Secretary of the US Air Force to simulate a one-on-one air battle. On May 2, U.S. Air Force Secretary Frank Kendall took off in an X-62AVISTA at Edwards Air Force Base. Note that during the one-hour flight, all flight actions were completed autonomously by AI! Kendall said - "For the past few decades, we have been thinking about the unlimited potential of autonomous air-to-air combat, but it has always seemed out of reach." However now,

This week, FigureAI, a robotics company invested by OpenAI, Microsoft, Bezos, and Nvidia, announced that it has received nearly $700 million in financing and plans to develop a humanoid robot that can walk independently within the next year. And Tesla’s Optimus Prime has repeatedly received good news. No one doubts that this year will be the year when humanoid robots explode. SanctuaryAI, a Canadian-based robotics company, recently released a new humanoid robot, Phoenix. Officials claim that it can complete many tasks autonomously at the same speed as humans. Pheonix, the world's first robot that can autonomously complete tasks at human speeds, can gently grab, move and elegantly place each object to its left and right sides. It can autonomously identify objects

The latest video of Tesla's robot Optimus is released, and it can already work in the factory. At normal speed, it sorts batteries (Tesla's 4680 batteries) like this: The official also released what it looks like at 20x speed - on a small "workstation", picking and picking and picking: This time it is released One of the highlights of the video is that Optimus completes this work in the factory, completely autonomously, without human intervention throughout the process. And from the perspective of Optimus, it can also pick up and place the crooked battery, focusing on automatic error correction: Regarding Optimus's hand, NVIDIA scientist Jim Fan gave a high evaluation: Optimus's hand is the world's five-fingered robot. One of the most dexterous. Its hands are not only tactile
