14 Most headaches for PHP beginners [1] The variables get, post, and session cannot be passed between pages. in the latest php version, automatic global variables are disabled, to obtain the submitted variables from the previous page, use $ _ GET [foo], $ _ POST [foo], $ _ SESSION [foo. Of course, you can also change the automatic global variable to open (php. ini is changed to register_glob, which is the most headache for PHP beginners.
[1] The get and post variables cannot be passed between pages. in the latest php version, automatic global variables are disabled, therefore, to obtain the submitted variables from the previous page, use $ _ GET ['foo'], $ _ POST ['foo'], $ _ SESSION ['foo. Of course, you can also change the automatic global variable to On (php. ini is changed to register_globals = On). considering compatibility, it is better to force yourself to get familiar with the new writing method.
[2] In Win32, an error occurs when apache2 uses the get method to pass Chinese parameters:
Test. php? A = Hello & B = you
Passing parameters will cause an internal error.
Solution: "test. php? A = ". urlencode (hello)." & B = ". urlencode (you can also)
.............
[3] The session under win32 does not work normally
Php. ini Default session. save_path =/tmp
This is obviously a configuration in linux. php in win32 cannot read or write session files, and thus the session cannot be used. you can change it to an absolute path, for example, session. save_path = c: windows emp.
[4] displaying error messages
When php. when display_errors = On and error_reporting = E_ALL of ini, all errors and prompts are displayed. it is best to enable this function during debugging for error correction, if you use php to write errors, most of them are about undefined variables. A prompt is displayed before the variable is assigned a value. The solution is to detect or block the variable.
For example, if $ foo is displayed, you can use if (isset ($ foo) echo $ foo or echo @ $ foo.
[5] Win32 mail () cannot send email
Sendmail configured in linux can be sent. In win32, you need to call the smtp server to send an email and modify php. SMTP = ip // ip address of ini is an smtp server without verification (hard to find online)
The best solution for sending emails in php is to directly send emails to the recipient's email server using socket instead of forwarding the server.
[6] If no password is set for the newly installed mysql instance, use update mysql. user set password = "yourpassword" where user = "root" to change the password.
[7] header already sent
This error usually occurs when you use the HEADER. it may be due to several reasons: 1. you PRING or ECHO before using the HEADER. 2. you have a blank line before the current file. 3. you may INCLUDE a file. this error may also occur if there are blank lines at the end of the file or the output .!
[8] php. ini has not changed.
Restart the web server, such as IIS and Apache, and then apply the latest settings.
[9] install php on 2003 (for how to install ISAPI, please advise)
Php4isapi. dll of PHP4 seems to be in conflict with 2003. it can only be installed in CGI mode.
Step 1: First install php-4.2.3-installer.exein www.php.net. you can also find the latest version. before installing php-4.2.3-installer.exe, ensure that your IIS6.0 is started and accessible. After installation, go to the default website --> application configuration.
Step 2: Click web service extension> Create web service extension.
Step 3: Add the extension --> php
Step 4: Find the php.exe path and add it.
Step 5: OK!
Step 6: Select the php service extension and click allow.
[10] sometimes SQL statements do not work, and database operations fail. the simplest debugging method is echo the SQL statement to see if the value of the variable can be obtained.
[11] Differences between include and require
There is no big difference between the two. if the file to be included does not exist, include prompts notice, and then continues to execute the following statement. require prompts a fatal error and exits.
According to my tests, on the win32 Platform, they are all included first and then executed. Therefore, it is recommended that there be no include or require statements in the contained files, which will cause directory confusion. Maybe * The situation is different in nux and has not been tested yet.
If you do not want to include a file multiple times, you can use include_once or require_once # to read and write document data.
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] Differences between isset () and empty ()
Both are used to test the variables, but isset () is used to test whether the variables are assigned values, and empty () is used to test whether a variable that has been assigned values is null.
If a variable is not assigned a value, it is allowed to be referenced in php, but there will be a notice prompt. if a variable is assigned a null value, $ foo = "" or $ foo = 0 or $ foo = false, empty ($ foo) returns true, and isset ($ foo) returns true, that is to say, assigning a null value does not cancel a variable.
To cancel a variable, you can use unset ($ foo) or $ foo = NULL.
[13] mysql Query statement contains keywords
When php queries mysql, sometimes the mysql table name or column name has a keyword, and the query will be wrong at this time. For example, if the table name is "order", an error will occur during the query. the simple method is to add '[ tab key above] to the table name or column name in the SQL statement, for example, select * from 'order'
[14] how to upload multiple files at a time through the HTTP protocol
There are two ways to implement the same method. The specific program also needs to be designed by yourself.
1. set multiple file input boxes in form and name them using arrays, as shown below:
<Form action = "" method = post>
<Input type = file name = usefile []>
<Input type = file name = usefile []>
<Input type = file name = usefile []>
</Form>
In this way, perform the following tests on the server:
Echo "<pre> ";
Print_r ($ _ FILES );
Echo "</pre> ";
2. set multiple file input boxes in form with different names, as shown below:
<Form action = "" method = post>
<Input type = file name = usefile_a>
<Input type = file name = usefile_ B>
<Input type = file name = usefile_c>
</Form>
Perform the same test on the server:
Echo "<pre> ";
Print_r ($ _ FILES );
Echo "</pre> ";
