


Explanation of the meaning of common PHP error prompts (practical! Worth collecting), error prompts worth collecting_PHP Tutorial
Explanation of the meaning of common PHP error prompts (practical! Worth collecting), error prompts are worth collecting
This article explains the meaning of common PHP error prompts. Share it with everyone for your reference, the details are as follows:
When I was learning PHP, I often encountered various error prompts. It felt good to see this error prompt and explanation today. I now turn it over for us to learn from. hehe. . . . .
1. Notice: Undefined variable: variable name in
Note: An undefined variable is used
2. Parse error: syntax error, unexpected T_ELSE in
If () {
}Else if () {
}
Echo $test;
Else {
}
Note: The if else if else sentence structure is wrong
3. Parse error: syntax error, unexpected $end in D
Note: Usually the curly braces do not match
4. Parse error: syntax error, unexpected T_STRING in
Note: Usually I forget to write the semicolon at the end of the sentence
5. Warning: Invalid argument supplied for foreach() in
Note: the first parameter of foreach must be an array
6. Warning: mysql_fetch_assoc(): supplied argument is not a valid MySQL result resource in
Note: This means that the previous execution of SQL failed to return. Generally, it may be an error in the SQL statement. If the analysis cannot come out, you can just print out Mysql_error (); to see where the error is specifically
7. No database selected
Note: Usually there is no connection to the database
8. Warning: mysql_connect() [function.mysql-connect]: Access denied for user 'root'@'localhost' (using password : YES) in ….. on line 3
Access denied for user 'root'@'localhost' (using password: YES)
Note: The database username and password are wrong
9. Unknown database 'cms07261′
Note: There is no such database
10. Table 'cms0726.test' doesn't exist
Note: The table does not exist
11. Unknown column 'abc' in 'field list'
Note: Field does not exist
12. Column count doesn't match value count at row 1
Note: The number of field values in the sql statement is different from the number of field names
13. Warning: Wrong parameter count for function name in
Note: The number of function logarithms is missing
14. Fatal error: Smarty error: [in message_list.html line 22]: syntax error: 'foreach: item' must be a variable name (literal string)
Note: Look at the line number, it means that the item after foreach must be followed by a variable name, without $, it is a string (note: no single or double quotes)
15. Fatal error: Smarty error: [in message_list.html line 24]: syntax error: unrecognized tag: msg.message_id
Note: $
16. Warning: Smarty error: unable to read resource: "message_list1.html" in
Note: The template file cannot be found. Check whether the file name is written incorrectly or the file is stored in another directory.
17. Fatal error: Cannot redeclare get_sort1() (previously declared in
Note: The function has been defined and cannot be redefined
I hope this article will be helpful to everyone in PHP programming.

PHPsessionscanstorestrings,numbers,arrays,andobjects.1.Strings:textdatalikeusernames.2.Numbers:integersorfloatsforcounters.3.Arrays:listslikeshoppingcarts.4.Objects:complexstructuresthatareserialized.

TostartaPHPsession,usesession_start()atthescript'sbeginning.1)Placeitbeforeanyoutputtosetthesessioncookie.2)Usesessionsforuserdatalikeloginstatusorshoppingcarts.3)RegeneratesessionIDstopreventfixationattacks.4)Considerusingadatabaseforsessionstoragei

Session regeneration refers to generating a new session ID and invalidating the old ID when the user performs sensitive operations in case of session fixed attacks. The implementation steps include: 1. Detect sensitive operations, 2. Generate new session ID, 3. Destroy old session ID, 4. Update user-side session information.

PHP sessions have a significant impact on application performance. Optimization methods include: 1. Use a database to store session data to improve response speed; 2. Reduce the use of session data and only store necessary information; 3. Use a non-blocking session processor to improve concurrency capabilities; 4. Adjust the session expiration time to balance user experience and server burden; 5. Use persistent sessions to reduce the number of data read and write times.

PHPsessionsareserver-side,whilecookiesareclient-side.1)Sessionsstoredataontheserver,aremoresecure,andhandlelargerdata.2)Cookiesstoredataontheclient,arelesssecure,andlimitedinsize.Usesessionsforsensitivedataandcookiesfornon-sensitive,client-sidedata.

PHPidentifiesauser'ssessionusingsessioncookiesandsessionIDs.1)Whensession_start()iscalled,PHPgeneratesauniquesessionIDstoredinacookienamedPHPSESSIDontheuser'sbrowser.2)ThisIDallowsPHPtoretrievesessiondatafromtheserver.

The security of PHP sessions can be achieved through the following measures: 1. Use session_regenerate_id() to regenerate the session ID when the user logs in or is an important operation. 2. Encrypt the transmission session ID through the HTTPS protocol. 3. Use session_save_path() to specify the secure directory to store session data and set permissions correctly.

PHPsessionfilesarestoredinthedirectoryspecifiedbysession.save_path,typically/tmponUnix-likesystemsorC:\Windows\TemponWindows.Tocustomizethis:1)Usesession_save_path()tosetacustomdirectory,ensuringit'swritable;2)Verifythecustomdirectoryexistsandiswrita


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