What are the common low-level errors in PHP programming?

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• Isset
  

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

When money is involved, a floating-point number is used to calculate, and then the monthly settlement will find that there will be a few dollars deviation, but the reconciliation is not found problems.

In fact, you should use integer to deal with.

Update, originally can use Bcmath library to solve this problem specifically, recommend https:// packagist.org/packages/ Webit/bcmath It's my fault I'm typing too fast ...

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

Re-build the wheel. For example, PHP provides functions to implement a function, but because they do not know, so they wrote a function to achieve the same function, not only waste time and increase the complexity of the code.

1. PlainText Access User password
   
2. Hard-coded and version-controlled password for background system
3. Non-encrypted cookies
4. "SELECT * from Users where id= ' {$_get[' uid ']} '"
5. Self-DDoS yourself foreach ($uids as $uid) {$service =: Connect ...; $service ...}
6. if (condition met) {...} no else, two months after discovery of mystery bug
7. If stream, if () {if () {if () {...}} if () {}}, do not reverse-determine the simplified code
8. Half a day in a view logic output a small piece of HTML
9. Easy to design class for the transfer of parameters
10. Use the SESSION as a NoSQL database, $_session["POST" [' title '] = ....
11. $data stream, $data =. If (..) $data, $data, $data ... Yi $data
12. To use class as a namespace, method is to set the function of class.
13. This $a->b[' C ' [' d '] [' e '] ... You don't have to isset.
14. Using Base64 as an encryption algorithm
15. Throw exception but lazy catch so that the error message appears in the HTTP response to let the user catch

I'm here without a semicolon, and I've come to this problem firsthand.
Once gave the customer a template, the error of this template let me speechless
Paste Code

   Echo "\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\"SetSource\"class=\"Pluszone\"> ";Echo $strPlusZone 4;Echo "\r\n\t\"S_setsource\"class=\"Pluszonex\">\r\n\t\"Sourcezone\">\r\n\t\r\n\t";Echo "
       
        ;
        Echo 
        "Cript>
        \r\n\t\$
        (document). Ready (function () {\ r
        \n\t\t\$
        (). Getpicsource ();
        \r\n\t
        });
        \r\n\t
        
        \r\n\t
        "
        ;
        }
        Echo 
        "
        \ t
        \"SourceName\"type=\"Hidden\"id=\"SourceName\"value=\"";Echo $sourcename;Echo "\"size=\" *\"/>\r\n\t\" Sourcefolder \" type= \" Hidden \" id= \" Sourcefolder \" value= \" " ; Echo $sourcefolder ;
       

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