Php basic programming FAQ summary This post was last edited by PhpNewnew at 18:33:34
Summary of common questions in this version. limited space answers may not be detailed enough. more answers are needed to make full use of the search engine.
The content of this post will be updated one after another. We hope to help more new users who need it. if you have any mistakes, please correct them.
1. how can I determine whether php is successfully installed and output related configuration environment parameters of php?
Answer: 1. create a php file, such as the file name phpinfo. php.
2. add code to the PHP file
3. open the file in the browser, localhost/phpinfo. php
If a detailed document appears normally, the installation is successful. if the above source code is directly output or the download file is not successful.
2. how to enable the php error prompt function? Disabled by default
A: In the php. ini file, change the search field error_reporting to error_reporting = E_ALL.
Display_errors is changed to display_errors = On. if there is # in front of the field, delete this annotator.
You need to restart apache to take effect. you can also add the code error_reporting (E_ALL) in the PHP file );
3. an error message similar to "Notice: Undefined index: xxx in..." is displayed.
A: This is a new change after version 5.3 (if you remember correctly). This is not an error, but a prompt.
The prompt indicates that the variable is used if it is not declared.
The solution can be:
A. disable the error prompt (or modify the error prompt level ). See FAQ 2 modify display_errors = Off
B. add if (issset ($ _ POST ['test']) before assigning values to submitted parameters, for example, $ _ POST ['test '].
Variable prompts can be replaced by initialization value assignment. for example, $ test = '';
4. garbled Chinese characters are output from the database or page, but there is no problem with English and numbers.
A: Generally, this problem is caused by encoding, so keeping all codes consistent is the solution to the problem.
Take gbk as an example
Php file header output header ("Content-Type: text/html; charset = gbk ");
Execute mysql_query ("set names 'gbk'") after connecting to the database in php '");
Set Database/table encoding to gbk
Whether the file encoding check is ANSI
5. how to build a php runtime environment?
A: We will have a detailed post to introduce this aspect. if you are a beginner, we recommend that you use integration.
The installation package to learn, because the php version is relatively large, if you only refer to the online teaching materials, it is easy to cause learning confusion.
Download the complete installation package for the following system and run the installation. for configuration problems, see the official help documentation.
Windows: http://www.apachefriends.org/zh_cn/xampp-windows.html
Http://www.apachefriends.org/zh_cn/xampp-linux.html: Linux
6. why do I use You can.
A: There is a short tag option in php. ini. open short_open_tag = On. remember to delete this annotator if there is # above.
This function is not recommended for individuals. please follow To write the code.
7. What are common php development tools?
A: If you like development tools that seem very professional and feature a wide range of functions
Eclipse zendstudio phpdesinger phpstorm netbeans...
If you like simplicity, the original development tools
Notepad ++ editplus ....
In Linux, there are basically all the Ides listed above, and Vim Gvim is available for simplicity...
8. what is the "flexibility" in the floating point number operation?
A: Warning
Floating point precision
Obviously, a simple decimal score is like 0.1 or 0.7. it cannot be converted to an internal binary format without losing a little precision. This will lead to chaotic results: for example, floor (0.1 + 0.7) * 10) usually returns 7 instead of 8 in expectation, because the internal representation of the result is similar to 7. 9999999999 ....
This is related to the fact that it is impossible to accurately express certain decimal scores with limited digits. For example, decimal 1/3 is changed to 0.3333333 ....
Therefore, never believe that the result of a floating point number is accurate to the last digit, or compare whether the two floating points are equal. If higher precision is required, use any precision mathematical function or gmp function.
9. the UTF8 encoded file session_start (), header (), settcookie () and other functions have an error and the system prompts "headers already sent ".
A: Generally, the UTF-8 encoding editor adds a three-byte BOM code to the file header to identify the UTF-8 encoding format. these three bytes are invisible to the normal file editor, the output is output in HTML first. The above error is prompted when you execute the above function. Solution: Use editplus to clear the BOM Editor and clear the BOM (set to utf8 to clear the BOM.
10. notes for coding mysql and php.
A: I need to remind you of the SET NAMES in mysql 'utf8'; there is no horizontal bar, and the correct php writing is UTF-8, many beginners in this place easy to get mixed puzzled, I hope to pay special attention to this small difference.
Reply to discussion (solution)
Thank you, Niu Ge.
Yes .. Niu hasn't had a holiday yet!
Yes .. Niu hasn't had a holiday yet!
Inniu is not on duty. why do we have a holiday? Hahaha
It's good to see this post early.
I learned how to list all my questions.
I really don't know the last one. I learned it ....
I am very helpful to new users. thank you.
When I saw the last article, I remember it was so miserable. Fortunately, I used the NOTEPAD ++ editor later and used the UTF8 function to clear BOM.
Ten years later, I think these problems are quite different.
Thank you.
Haha. Another gentle knowledge. Thank you!
9th questions
How can I use notepad?
Don't want to use editplus
Well organized. thank you for sharing.
9th questions
How can I use notepad?
Don't want to use editplus
How do you do this...
These problems have basically been encountered
I learned. I just got a student ··
After learning, I want to find a PHP development tool.
Very useful
Looking back at the time when Google was constantly developing Niang, inniu was full of faces.
Sorry, it's all about basics. I learned it!
I learned and learned something.
Common and classic problems
Thank you! For beginners!
Thank the moderator for learning.
I learned
Look .....
Very good. I have been confused about some questions, but I have not found the answer. today I am finally confused.
It seems that the ninth line has written a wrong function name settcookie (). it should be setcookie (). I am a beginner and I don't know if it is correct.
If it is the first problem, I have installed it works in apache, that is, the PHP file cannot run. how can this problem be solved?
It is difficult for beginners to understand.
Supported and useful
4. garbled Chinese characters are output from the database or page, but there is no problem with English and numbers.
A: Generally, this problem is caused by encoding, so keeping all codes consistent is the solution to the problem.
Take gbk as an example
Php file header output header ("Content-Type: text/html; charset = gbk ");
Execute mysql_query ("set names 'gbk'") after connecting to the database in php '");
Set Database/table encoding to gbk
Whether the file encoding check is ANSI
Correct this. you do not need to set the database/table encoding to gbk. mysql will automatically convert the database/table encoding because of the preceding set names gbk statement. of course, the database/table encoding must have a conversion relationship with gbk, such as gb2312 and utf8.
Update.
Good post ,? I?
