What are common low-level errors in PHP programming? -Php Tutorial

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• Isset
  

$a = null;var_dump(isset($a)); //false

When money is involved, floating point numbers are used for calculation, and then the deviation of a few dollars is found during monthly settlement, but the reconciliation cannot be found.

In fact, Integer should be used for processing.

Update, originally can use bcmath library to specifically solve this problem, recommended https://packagist.org/packages/webit/bcmath All blame me for typing too fast...

$result = $this->select();return $reuslt;

Repeat the wheel. For example, PHP provides a function to implement a function, but because I don't know it, I wrote another function to implement the same function, which not only wastes time but also increases the complexity of the code.

1. Plaintext access user password
   
2. Password for hardcoded and version-controlled background systems
3. Unencrypted cookie
4. "SELECT * FROM users where id = '{_ _ GET ['uid']}'"
5. Self-DDOS foreach ($ uids as $ uid) {$ service =... connect ...... $ service ...}
6. If (condition met) {...} no else, a mysterious bug found two months later
7. If stream, if () {...} if () {}} without reverse judgment to simplify the code
8. In a view, a short section of html is output logically for half a day.
9. Design Class for parameter passing convenience
10. Use SESSION as a NOSQL database, $ _ SESSION ["post"] ['title'] = ....
11. $ Data stream, $ data =... if (...) $ data, $ data, $ data... all the way $ data
12. When Class is used as the namespace, method sets the function of Class.
13. In this way, $ a-> B ['c'] ['D'] ['E ']...
14. Use base64 as the encryption algorithm
15. Throw exception, but too lazy to catch, so that the error message appears in the http response to allow the user to catch

I am here without a semicolon. I have personally experienced this problem.
When I used to give the customer a template, the template error left me speechless
Post Code

  \r\n\t\t
\r\n\t
\r\n\t\r\n\t";if ( $sourceurl != "-1" && $sourceurl != "" && $sourceurl != "0" && strstr( $sourceurl, "/" ) ){$SourceArr = explode( "/", $sourceurl );$sourcename = $SourceArr[1];$sourcefolder = $SourceArr[0];echo "\t
";echo $strPlusZone4;echo "
\r\n\t
\r\n\t
\r\n\t
\r\n\t";echo "
  
   \r\n\t\$(document).ready(function(){\r\n\t\t\$().getPicSource();\r\n\t});\r\n\t《script》\r\n\t";}echo "\t
   \r\n\t