Home Backend Development PHP Tutorial A summary of fourteen problems that cause headaches for PHP beginners_PHP Tutorial

A summary of fourteen problems that cause headaches for PHP beginners_PHP Tutorial

Jul 21, 2016 pm 03:49 PM
get php post session transfer beginner ten variable big Summarize question page

1. Variables cannot be transferred between pages
The automatic global variables of get, post, and session are turned off in the latest PHP version, so to get the submitted variables from the previous page, use $_GET ['foo'],$_POST['foo'],$_SESSION['foo'] to get. Of course, you can also modify the automatic global variables to be on (php.ini is changed to register_globals = On); considering compatibility, it is better to force yourself to become familiar with the new writing method.
2. Using the get method to pass Chinese parameters to apache2 under Win32 will cause an error
test.php?a=Hello&b=Hello
Passing parameters will cause an internal error
Solution: "test.php?a=".urlencode(Hello)."&b=".urlencode(Hello)
...
3. Win32 The session does not work properly
php.ini default session.save_path = /tmp
This is obviously the configuration under Linux. PHP cannot read and write the session file under win32, causing the session to be unusable
Put it away Just change it to an absolute path, for example, session.save_path = c:windowstemp
4. Display error message
When display_errors in php.ini = On and error_reporting = E_ALL, it will be displayed It is best to turn on all errors and prompts during debugging for error correction. If you use the previous PHP writing method, most of the error messages are about undefined variables. There will be a prompt when a variable is called before it is assigned a value. The solution is to detect or shield it.
For example, to display $foo, you can if(isset($foo)) echo $foo or echo @$foo
5. Mail() cannot send emails under Win32
In Linux The configured sendmail can be sent. Under win32, you need to call the smtp server to send emails. Modify the SMTP of php.ini = ip //ip is an smtp server without verification function (hard to find on the Internet), and php sends emails. The best solution is to use socket to send directly to the other party's email server without forwarding the server.
6. If the password is not set for the initial installation of mysql, you should use
update mysql.user set password="yourpassword" where user="root"
Change password
7. header already sent
This error usually occurs when you use HEADER. It may be due to several reasons: 1. You PRING or ECHO before using HEADER. 2. There is something in front of your current file. Blank line 3. You may have INCLUDEd a file and there is a blank line at the end of the file or this error will occur in the output.
8. There is no change after changing php.ini
Restart the web server, such as IIS, Apache, etc., and then the latest settings will be applied
9. php in Installation on 2003 (I urge experts to advise on the ISAPI installation method)
PHP4’s php4isapi.dll seems to conflict with 2003, and can only be installed in CGI mode:
Step 1, first download to www.php.net An installation program
10. Sometimes the sql statement does not work and the database operation fails
The easiest debugging method is to echo the sql sentence and see if the value of the variable can be obtained.
11. The difference between include and require
There is not much difference between the two. If the file to be included does not exist, include will prompt a notice, and then continue to execute the following statement, and require will prompt a fatal error. And exit. According to my test, under the win32 platform, they are included first and then executed, so it is best not to have include or require statements in the included files, which will cause directory confusion. Maybe the situation is different in *nux, I haven’t tested it yet
If you don’t want a file to be included multiple times, you can use include_once or require_once## to read and write document data:

Copy Code The code is as follows:

function r($file_name) {
$filenum=@fopen($file_name,"r");
@flock($ filenum,LOCK_SH);
$file_data=@fread($filenum,filesize($file_name));
@fclose($filenum);
return $file_data;
}
function w ($file_name,$data,$method="w"){
$filenum=@fopen($file_name,$method);
flock($filenum,LOCK_EX);
$file_data=fwrite( $filenum,$data);
fclose($filenum);
return $file_data;
}

12. The difference between isset() and empty()
Both are used to test variables.
But isset() tests whether a variable has been assigned a value, while empty() tests whether a variable that has been assigned a value is empty. If a variable is referenced in PHP without being assigned a value, it is allowed, but there will be a notice. If a variable is assigned a null value, $foo="" or $foo=0 or $foo=false, then empty($foo) returns true and isset($foo) also returns true, which means assigning a null value will not log out. a variable.
To unregister a variable, you can use unset($foo) or $foo=NULL.
13. The mysql query statement contains keywords
When PHP queries mysql, sometimes the mysql table name or column name contains keywords. There will be errors in the query at this time. For example, if the table name is order, an error will occur during query. The simple way is to add `[above the tab key] to the table name or column name in the sql statement to distinguish it,
for example, select * from `order`.
14. Method of uploading multiple files at one time through HTTP protocol
There are two ideas, which are two implementations of the same method. The specific procedures need to be designed by yourself:
1. Set up multiple file input boxes in the form and name them with arrays, as follows:

< ;input type=file name=usefile[]>



In this way, do the following tests on the server side
echo "

1

"; <br>print_r($_FILES); <br>echo "

";
2. Set multiple file input boxes in the form, but with different names, as follows:





Do the same test on the server side:
echo "

1

"; <br>print_r($_FILES); <br>echo "

";
Preface,
I installed: php-4.2.3-installer.exe, you can also find the latest one version, make sure your IIS6.0 is started and accessible before installing php-4.2.3-installer.exe. After installation, go to the default website-->Application configuration;
Step 2: Click web service extension-->New web service extension;
Step 3: Extension-->php, and then add ;
Step 4: Find the path to php.exe and add it;
Step 5: Confirm;
Step 6: Select the PHP service extension and click Allow.​

www.bkjia.comtruehttp: //www.bkjia.com/PHPjc/319595.htmlTechArticle1. Variables get, post, and session cannot be passed between pages. In the latest PHP version, automatic global variables are turned off. Yes, so to get the submitted variables from the previous page, use $_GET['foo']...
Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

AI Hentai Generator

AI Hentai Generator

Generate AI Hentai for free.

Hot Tools

Notepad++7.3.1

Notepad++7.3.1

Easy-to-use and free code editor

SublimeText3 Chinese version

SublimeText3 Chinese version

Chinese version, very easy to use

Zend Studio 13.0.1

Zend Studio 13.0.1

Powerful PHP integrated development environment

Dreamweaver CS6

Dreamweaver CS6

Visual web development tools

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)

PHP 8.4 Installation and Upgrade guide for Ubuntu and Debian PHP 8.4 Installation and Upgrade guide for Ubuntu and Debian Dec 24, 2024 pm 04:42 PM

PHP 8.4 brings several new features, security improvements, and performance improvements with healthy amounts of feature deprecations and removals. This guide explains how to install PHP 8.4 or upgrade to PHP 8.4 on Ubuntu, Debian, or their derivati

How To Set Up Visual Studio Code (VS Code) for PHP Development How To Set Up Visual Studio Code (VS Code) for PHP Development Dec 20, 2024 am 11:31 AM

Visual Studio Code, also known as VS Code, is a free source code editor — or integrated development environment (IDE) — available for all major operating systems. With a large collection of extensions for many programming languages, VS Code can be c

7 PHP Functions I Regret I Didn't Know Before 7 PHP Functions I Regret I Didn't Know Before Nov 13, 2024 am 09:42 AM

If you are an experienced PHP developer, you might have the feeling that you’ve been there and done that already.You have developed a significant number of applications, debugged millions of lines of code, and tweaked a bunch of scripts to achieve op

How do you parse and process HTML/XML in PHP? How do you parse and process HTML/XML in PHP? Feb 07, 2025 am 11:57 AM

This tutorial demonstrates how to efficiently process XML documents using PHP. XML (eXtensible Markup Language) is a versatile text-based markup language designed for both human readability and machine parsing. It's commonly used for data storage an

Explain JSON Web Tokens (JWT) and their use case in PHP APIs. Explain JSON Web Tokens (JWT) and their use case in PHP APIs. Apr 05, 2025 am 12:04 AM

JWT is an open standard based on JSON, used to securely transmit information between parties, mainly for identity authentication and information exchange. 1. JWT consists of three parts: Header, Payload and Signature. 2. The working principle of JWT includes three steps: generating JWT, verifying JWT and parsing Payload. 3. When using JWT for authentication in PHP, JWT can be generated and verified, and user role and permission information can be included in advanced usage. 4. Common errors include signature verification failure, token expiration, and payload oversized. Debugging skills include using debugging tools and logging. 5. Performance optimization and best practices include using appropriate signature algorithms, setting validity periods reasonably,

PHP Program to Count Vowels in a String PHP Program to Count Vowels in a String Feb 07, 2025 pm 12:12 PM

A string is a sequence of characters, including letters, numbers, and symbols. This tutorial will learn how to calculate the number of vowels in a given string in PHP using different methods. The vowels in English are a, e, i, o, u, and they can be uppercase or lowercase. What is a vowel? Vowels are alphabetic characters that represent a specific pronunciation. There are five vowels in English, including uppercase and lowercase: a, e, i, o, u Example 1 Input: String = "Tutorialspoint" Output: 6 explain The vowels in the string "Tutorialspoint" are u, o, i, a, o, i. There are 6 yuan in total

Explain late static binding in PHP (static::). Explain late static binding in PHP (static::). Apr 03, 2025 am 12:04 AM

Static binding (static::) implements late static binding (LSB) in PHP, allowing calling classes to be referenced in static contexts rather than defining classes. 1) The parsing process is performed at runtime, 2) Look up the call class in the inheritance relationship, 3) It may bring performance overhead.

What are PHP magic methods (__construct, __destruct, __call, __get, __set, etc.) and provide use cases? What are PHP magic methods (__construct, __destruct, __call, __get, __set, etc.) and provide use cases? Apr 03, 2025 am 12:03 AM

What are the magic methods of PHP? PHP's magic methods include: 1.\_\_construct, used to initialize objects; 2.\_\_destruct, used to clean up resources; 3.\_\_call, handle non-existent method calls; 4.\_\_get, implement dynamic attribute access; 5.\_\_set, implement dynamic attribute settings. These methods are automatically called in certain situations, improving code flexibility and efficiency.

See all articles