这回真的是挤时间了-PHP基础(三)
hi
刚看了唐人街探案,5星好评啊亲。由于是早就约好的,也不好推辞(虽然是和男的..),但该写的还是得挤时间写。明天早上老师的项目结题,虽然和我关系不大,但不要添乱就好!!
1、PHP
一、PHP基础(三)
1.3.2 Int
整型。
几个点:进制问题(2,8,16);
溢出——溢出后自动转为float型;
整除;
float转为int——向下取整;
例子给出
$shi=123;
$bin=0b100001;
$ba=0123;
$shiliu=0x1234555;
function show($a){
echo "Truth is:";
var_dump($a);
echo "
";
}
show($shiliu);
show($ba);
show($bin);
$qiguaideba=01237823; //八进制的“溢出”,会截断,只输出01237
show($qiguaideba);
function zhengchu($a,$b){
$c=$a/$b;
if(is_float($c)){
var_dump(round($c)); //用round控制输出结果
}else{
var_dump($c);
}
}
zhengchu($shiliu , $ba);
1.3.3 float
php版本不同,浮点型的精确度似乎是有变化的;而且坑爹的是,由于PHP内部机制的问题,也许会出现:
var_dump(floor((0.1+0.7)*10));
返回的往往是7而不是期望中的8....
使用高精度的话,用gmp函数,请自行去了解...
然后真想比较的话,不妨设置一个最小值来比较:
$bijiao1=0.232342342;
$bijiao2=0.232342323;
$esp=0.000001;
if(abs($bijiao1-$bijiao2) echo "True"."
";
}else{
echo "F**k"."
";
}
1.3.4 字符串
单双引号括起来的就是了~
然后只想说一点的就是heredoc:
$str=
alsidjflja
akjsdhflkj
dfjlkj.
EOF;
echo $str;
基本就是这么个样子,但是注意,最后一行那个EOF;是必须要和分号紧紧相依的,而且分号后面必须是换行,EOF前面不能出现包括空格的一切东西;
然后heredoc还可以用在传递参数,初始化静态值等等;
当然,heredoc中也可以调用参数啊属性的什么的——把EOF看成是大大的双引号就好了。
其他的字符串相关,比如我经常用到的.做连接符什么的,比较基础,但是好用,去看一下视频就很明了。
nowdoc也是一种比较新的方式,不太熟悉,然后似乎相当于单引号。
1.4 变量
变量好用,变量灵活,变量难用——一般就是渐渐的这么认为的。
第一,PHP中不强调赋初值,不需要声明,但是推荐还是赋初值,养成好习惯;不赋初值,变量值为其类型的默认值;
第二,引用赋值要知道,$b=&$a; 只能对变量名进行操作;
第三,赋值一次更新一次:
$shit="asdf";
$s=123;
echo $shit;
$shit=$s;
echo $shit;
2、GD库实现图片水印与缩略图
一、简介
使用PHP中自带的GD库制作图片的水印。
适合大批量的图片的简单处理。
学习基本的方法,然后封装为一个工具类。
这周末除了看星球大战,就来补过补过,知道错了。。。。。

TomodifydatainaPHPsession,startthesessionwithsession_start(),thenuse$_SESSIONtoset,modify,orremovevariables.1)Startthesession.2)Setormodifysessionvariablesusing$_SESSION.3)Removevariableswithunset().4)Clearallvariableswithsession_unset().5)Destroythe

Arrays can be stored in PHP sessions. 1. Start the session and use session_start(). 2. Create an array and store it in $_SESSION. 3. Retrieve the array through $_SESSION. 4. Optimize session data to improve performance.

PHP session garbage collection is triggered through a probability mechanism to clean up expired session data. 1) Set the trigger probability and session life cycle in the configuration file; 2) You can use cron tasks to optimize high-load applications; 3) You need to balance the garbage collection frequency and performance to avoid data loss.

Tracking user session activities in PHP is implemented through session management. 1) Use session_start() to start the session. 2) Store and access data through the $_SESSION array. 3) Call session_destroy() to end the session. Session tracking is used for user behavior analysis, security monitoring, and performance optimization.

Using databases to store PHP session data can improve performance and scalability. 1) Configure MySQL to store session data: Set up the session processor in php.ini or PHP code. 2) Implement custom session processor: define open, close, read, write and other functions to interact with the database. 3) Optimization and best practices: Use indexing, caching, data compression and distributed storage to improve performance.

PHPsessionstrackuserdataacrossmultiplepagerequestsusingauniqueIDstoredinacookie.Here'showtomanagethemeffectively:1)Startasessionwithsession_start()andstoredatain$_SESSION.2)RegeneratethesessionIDafterloginwithsession_regenerate_id(true)topreventsessi

In PHP, iterating through session data can be achieved through the following steps: 1. Start the session using session_start(). 2. Iterate through foreach loop through all key-value pairs in the $_SESSION array. 3. When processing complex data structures, use is_array() or is_object() functions and use print_r() to output detailed information. 4. When optimizing traversal, paging can be used to avoid processing large amounts of data at one time. This will help you manage and use PHP session data more efficiently in your actual project.

The session realizes user authentication through the server-side state management mechanism. 1) Session creation and generation of unique IDs, 2) IDs are passed through cookies, 3) Server stores and accesses session data through IDs, 4) User authentication and status management are realized, improving application security and user experience.


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

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

Hot Article

Hot Tools

Safe Exam Browser
Safe Exam Browser is a secure browser environment for taking online exams securely. This software turns any computer into a secure workstation. It controls access to any utility and prevents students from using unauthorized resources.

SublimeText3 Chinese version
Chinese version, very easy to use

VSCode Windows 64-bit Download
A free and powerful IDE editor launched by Microsoft

Atom editor mac version download
The most popular open source editor

SublimeText3 English version
Recommended: Win version, supports code prompts!
