What kind of tennis racket should a beginner buy? The fourteen most troublesome questions for PHP beginners

[1] Variables cannot be transferred between pages. Get, post, and session automatic global variables are turned off in the latest PHP version, so to get 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】 When apache2 uses the get method to pass Chinese parameters under Win32, an error will occur:
　 test.php?a=Hello&b=你好
　 Passing parameters will cause an internal error
　 Solution: "test.php?a= ".urlencode(Hello)."&b=".urlencode(Hello)
　　 .............
　【3】Session under win32 does not work properly
　 php.ini default session.save_path = /tmp
　This is obviously a configuration under Linux. PHP cannot read and write session files under win32, causing the session to be unusable. Just change it to an absolute path. For example, session.save_path = c:Windows emp
　　 [ 4】Display error information
When display_errors of 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, the error message is mostly about the future. Define 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
　 Sendmail configured under Linux can be sent, but 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 it directly to the other party email server without forwarding 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 appear for 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 have INCLUDEd a file and there is a blank line at the end of the file or the output will also appear This kind of mistake. !
　【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 kindly requested by experts)
　 The php4isapi.dll of PHP4 seems to have some conflicts with 2003, and can only be installed in CGI mode
　 Step 1, first install it under www.php.net The program I installed is: php-4.2.3-installer.exe. You can also find the latest version. Before installing php-4.2.3-installer.exe, make sure that your IIS6.0 is started and can access. 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 a 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 a file does not want 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 It is used to test variables, but isset() tests whether a variable has been assigned a value, and empty() tests whether a variable that has been assigned a value is empty.
　 If a variable is referenced in PHP without being assigned a value, it is allowed, but there will be a notice prompt. If a variable is assigned an empty value, $foo="" or $foo=0 or $foo=false, then empty( $foo) returns true, isset($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 $foo=NULL
　 【13】 Mysql query statement contains keywords
　 When PHP queries mysql, sometimes the mysql table name or column name has keywords. This Sometimes there will be errors in the query. For example, if the table name is order, an error will occur during the query. The simple way is to add `[above the tab key] to the table name or column name in the sql statement to distinguish it, for example, select * from `order`
　 【14】 Once through the HTTP protocol There are two ideas for uploading multiple files, which are two implementations of the same method. The specific procedures need to be designed by yourself.
　 1. Set up multiple file input boxes in the form and name them with arrays, as follows:
＜form action="" method=post＞
＜input type=file name=usefile[]＞
＜input type= file name=usefile[]＞
＜input type=file name=usefile[]＞
＜/form＞
　 In this way, do the following tests on the server side:
echo "＜pre＞";
print_r($_FILES);
echo "＜/pre＞";
　 2. Set multiple file input boxes in the form, 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);

The above introduces what tennis racket should beginners buy? The fourteen most troublesome questions for PHP beginners, including what tennis racket should beginners buy. I hope it will be helpful to friends who are interested in PHP tutorials.