The fourteen most troublesome problems for PHP beginners

[1] Variables get, post, and session cannot be transferred between pages. In the latest PHP version, automatic global variables are turned off, 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 is 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 to apache2 under Win32 will cause an error:

test.php?a=Hello&b=Hello.

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.

php.ini default session.save_path = /

tmp Obviously it is a configuration under Linux. PHP under win32 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 php.ini When display_errors = 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.

Sendmail configured under Linux can send, but you need to call smtp under win32. The server is used to send emails, modify the SMTP of php.ini = ip //ip is an smtp server without verification function (hard to find online).

The best solution for sending emails in php is to use socket to send directly to the other party's email server instead of 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]

The header already sent error usually occurs when you use HEADER. There may be 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 this error will occur in the output . !

【8】After changing php.ini and there is no change,

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

[9] PHP is installed on 2003 (I would like to ask experts for advice on how to install ISAPI).

The php4isapi.dll of PHP4 seems to have some conflicts with 2003. It can only be installed in CGI mode.

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

Step 2: Click web service extension-->New web service extension.

Step 3: Extension-->php, then add

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

Step Five: Confirm and that’s it!

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.

There is not much difference between

include and require

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 do not 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()

is that both are used to test variables, but isset() tests whether a variable has been assigned a value, while 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 a null 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] The mysql query statement contains keywords.

When php queries mysql, sometimes the mysql table name or column name has keywords. At this time, the query will There are errors. 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] One-time upload through HTTP protocol

for the method of multiple files

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

1. Set multiple file input boxes in the form and name them in 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 test 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);
echo "＜/pre＞";