The Fourteen Most Confusing Problems for PHP Beginners_PHP Tutorial

[1] Variables cannot be transferred between pages. Get, post, and session automatic global variables are turned off in the latest PHP version. Therefore, to obtain the submitted variables from the previous page, use $_GET['foo'], $_POST. ['foo'],$_SESSION['foo'] to get. Of course, you can also modify the automatic global variables to be on (php.ini changed to register_globals = On); considering compatibility, it is better to force yourself to become familiar with the new writing method.
[2] Using the get method to pass Chinese parameters in apache2 under Win32 will cause an error:

test.php?a=Hello&b=你好

Passing parameters will cause an internal Error

Solution: "test.php?a=".urlencode(Hello)."&b=".urlencode(Hello)

........... .....

【3】The session under win32 does not work properly

The default session.save_path in php.ini = /tmp

This is obviously under linux Configuration, under win32, PHP cannot read and write the session file, causing the session to be unusable. Just change it to an absolute path, for example, session.save_path = c:windows emp

【4】Display error message

When display_errors in php.ini = On and error_reporting = E_ALL, all errors and prompts will be displayed. It is best to turn it on during debugging for error correction. If you use the previous PHP writing method, most of the error messages are about undefined variables. . There will be a prompt when a variable is called before it is assigned a value. The solution is to detect or shield it.

For example, to display $foo, you can if(isset($foo)) echo $foo or echo @$foo

【5】mail() cannot send emails under Win32

The sendmail configured under Linux can be sent. Under win32, you need to call the SMTP server to send emails. Modify the SMTP of php.ini = ip //ip is an SMTP server without verification function (hard to find on the Internet)

The best solution for sending emails in PHP is to use socket to send directly to the other party’s email server without forwarding the server.

【6】If the password is not set for the initial installation of mysql, you should 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 HEADER. It may be due to several reasons: 1. You PRING or ECHO before using HEADER 2. There is a blank line in front of your current file 3. You may INCLUDE This error will also occur if a file is created and there is a blank line at the end of the file or the output is output. !

　【8】No change after changing php.ini

　 Restart the web server, such as IIS, Apache, etc., and then the latest settings will be applied.

[9] PHP is installed on 2003 (the installation method of ISAPI is requested by experts for advice)

PHP4’s php4isapi.dll seems to conflict with 2003 and can only be installed in CGI mode

Step 1: First download an installation program from www.php.net. I installed: php-4.2.3-installer.exe. You can also find the latest version and install php-4.2.3- Before installing installer.exe, make sure your IIS6.0 is started and accessible. After installation, go to the default website-->Application configuration.

Step 2: Click web service extension --> Create a new web service extension.

Step 3: Extension-->php, then add

Step 4: Find the path to php.exe and add it.

Step 5: Just confirm!

Step 6: Select the PHP service extension and click Allow.

[10] Sometimes the sql statement does not work and the database operation fails. The easiest way to debug is to echo the sql sentence and see if the value of the variable can be obtained.

【11】The difference between include and require

There is not much difference between the two. If the file to be included does not exist, include will prompt notice, and then continue to execute the following statement, require will prompt fatal error and exit.

According to my testing, under the win32 platform, they are included first and then executed, so it is best not to have include or require statements in the included files, which will cause directory confusion. Maybe the situation is different under *nux, I haven't tested it yet.

If you don’t want a file to be included 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] The difference between isset() and empty()

Both are used to test variables, but isset( ) is to test whether a variable has been assigned a value, while empty() is to test whether a variable that has been assigned a value is empty.

If a variable is not assigned a value, it is allowed to be referenced in PHP, but there will be a notice that if a variable is assigned a null value, $foo="" or $foo=0 or $foo= false, then empty($foo) returns true and isset($foo) also returns true, which means assigning a null value will not unregister a variable.

To unregister a variable, you can use unset($foo) or $foo=NULL

[13] The mysql query statement contains keywords

When php queries mysql , sometimes there are keywords in the mysql table name or column name, and then there will be errors in the query. For example, if the table name is order, an error will occur during the query. The simple way is to add `[above the tab key] to the table name or column name in the SQL statement to distinguish it, for example, select * from `order`

　[14 】The method of uploading multiple files at one time through HTTP protocol

There are two ideas, which are two implementations of the same method. The specific procedures need to be designed by yourself.

1. Set up multiple file input boxes in the form and name them with arrays, 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, Do the following tests on the server side:

echo "＜pre＞";
print_r($_FILES);
echo "＜/pre＞";

2. In the form Set multiple file input boxes in , but with different names, 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＞

Do the same test on the server side:

echo "＜pre＞";
print_r($_FILES);
echo "＜/pre＞";