14 things that cause headaches for PHP beginners

Today, we will give you a big Summary of the headaches for PHP beginners. The 14 questions raised below hope to help PHP beginners.

1. Variables cannot be transferred between pages.

The get, post, and session automatic global variables are disabled in the latest PHP version. Therefore, to obtain and submit the 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. An error occurs when apache2 uses the get method to pass Chinese parameters under Win32.

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 in Win32 cannot work normally.

PHP. ini default session. save_path =/tmp

This is obviously a configuration in Linux. in Win32, PHP cannot read or write session files, and thus the session cannot be used.

Change it to an absolute path, for example, session. save_path = C:/Windows/temp.

4. Display 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. Email cannot be sent by mail () under Win32

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 (difficult to find on the Internet ), 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 the password is not set for the newly installed MySQL instance, use

Update mysql. User SET Password = "yourpassword" where user = "root"

Change 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: click 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 variable value 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 continues executing the following statement. Require prompts a fatal error and exits. According to my test, on the Win32 platform, they are all included first and then executed. Therefore, it is best not to have include or require statements in the contained files, which will cause directory confusion. Maybe * Nux is different. It hasn't 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 the file data:

Reference content is as follows:
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;
}
Www.devdao.com
 

12. Differences between isset () and empty ()

Both are used to test variables.

However, isset () is used to test whether a variable is assigned a value, while empty () is used to test whether a variable that has been assigned a value is null. If a variable is not assigned a value, it is allowed to reference it 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, isset ($ Foo) returns the true value, that is, the null value will not cancel a variable.

To cancel a variable, you can use unset ($ Foo) or $ Foo = NULL.

13. MySQL query statements contain keywords

When PHP queries MySQL, sometimes the MySQL table name or column name has keywords. At this time, the query will have an error. For example, if the table name is order, an error occurs during query. The simple method is to add '[tab top] to the table name or column name in the SQL statement to differentiate them,

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 procedures also need to be designed by yourself:

1. Set multiple file input boxes in form and name them using arrays, as shown below:

Reference content is as follows:
<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 side:
Echo "<PRE> ";
Print_r ($ _ files );
Echo "</PRE> ";
 

2. Set multiple file input boxes in form with different names, as shown below:

Reference content is as follows:
<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> ";