Summary of some common problems in Php_PHP tutorial

Summary of some common problems in Php 1: Why can’t I get the variable

I POST data name from one web page to another web page, why can’t I get any value when I output $name?

After PHP 4.2 In this version, register_global defaults to off
If you want to get the variables submitted from another page:

Method 1: Find register_global in PHP.ini and set it to on.
Method 2: Put this extract($_POST);extract($_GET); at the front of the receiving webpage (note that there must be Session_Start() before extract($_SESSION)).
Method 3: Read variables $a= one by one $_GET["a"];$b=$_POST["b"], etc. Although this method is troublesome, it is safer.

2: Debug your program

while it is running You must know the value of a variable.This is what I did, create a file debug.php with the following content:

PHP code:------------------------ -------------------------------------------------- ------

Ob_Start();
Session_Start();
Echo "

";<br><br>Echo "this The _GET variables obtained by this page are: ";<br>Print_R($_GET);<br><br>Echo "The _POST variables obtained by this page are: ";<br>Print_R($_POST);<br> <br>Echo "The _COOKIE variables obtained on this page are:";<br>Print_R($_COOKIE);<br><br>Echo "The _SESSION variables obtained on this page are:";<br>Print_R($ _SESSION);<br>Echo "

";
?>

----------------------- -------------------------------------------------- -------

Then set include_path = "c:/php" in php.ini, and put debug.php in this folder.
You can then set it in each This file is included in the web page and you can view the variable names and values.

3: How to use session

Anything related to session must call the function session_start();

Paying value for the session is very simple, such as:


PHP code:-------------------------------- -------------------------------------------------- -

Session_start();
$Name = "This is a Session example";
Session_Register("Name");//Note, do not write: Session_Register ("$Name");
Echo $_SESSION["Name"];
//Then $_SESSION["Name"] is "This is a Session example"
?>

------------------------------------------------ --------------------------------



After php4.2, You can pay directly for the session:

PHP code: ---------------------------------- --------------------------------------------------

Session_Start();
$_SESSION["name"]="value";
?>

--------- -------------------------------------------------- --------------------

Cancel the session like this:

PHP code:---------- -------------------------------------------------- --------------------

session_start();
session_unset();
session_destroy() ;
?>

------------------------------------- --------------------------------------------------


There is a BUG in canceling a certain session variable in php4.2 and above.



Note:

1: There cannot be any output before calling Session_Start(). For example The following is wrong.
============================================
1 line
2 lines3 lines Session_Start();//There was already output in the first line before
4 lines...
5 lines?> ;
============================================


Tip 1:

Any time ".....headers already sent....." appears, it means that information is output to the browser before Session_Start() .
It will be normal if you remove the output, (this error will also occur in COOKIE, the cause of the error is the same)

Tip 2:

If your Session_Start() is placed in a loop statement, and It is difficult to determine where the information was output to the browser before. You can use the following method:
Line 1
.....Here is your program ......



2: What is this error

Warning: session_start(): open(/tmpsess_7d190aa36b4c5ec13a5c1649cc2da23f, O_RDWR) failed:....
Because you did not specify the storage path of the session file.

Solution:
(1) Create the folder tmp on the c drive
(2) Open php.ini and find session.save_path, Modify to session.save_path= "c:/tmp"



4: Why when I transfer variables to another web page, I only get the first half, and all the ones starting with spaces are lost


PHP code:---------------------------------------- ----------------------------------------

$Var="hello php";//Change to $Var=" hello php"; Try to get the result
$post= "receive.php?Name=".$Var;
header ("location:$post");
?>

----------------------------- -------------------------------------------------- -

receive.php content:

PHP code:------------------------------- -------------------------------------------------- --

Echo "

";<br>Echo $_GET["Name"];<br>Echo "

";
?>

----------------------------------------- ---------------------------------------


Correct The method is:

PHP code:----------------------------------------- ------------------------------------------

< ?php
$Var="hello php";
$post= "receive.php?Name=".urlencode($Var);
header("location:$post");
?>

----------------------------------------- ---------------------------------------


Receiving You don't need to use Urldecode() on the page, the variables will be automatically encoded.


5: How to intercept Chinese characters of a specified length without ending with "?>", and the excess part will end with "..." Replace


Generally speaking, the variable to be intercepted comes from Mysql. First, you must ensure that the field length is long enough, usually char(200), which can hold 100 Chinese characters, including punctuation.

PHP code:-------------------------------------------------- ------------------------------------

$ str="This character is so long,^_^";
$Short_Str=showShort($str,4);//Intercept the first 4 Chinese characters, the result is: this character...
Echo "$Short_Str";
Function csubstr($str,$start,$len )
{
$strlen=strlen($str);
$clen=0;
for($i=0;$i<$strlen;$i++,$clen++)
{
if ($clen>=$start+$len)
break;
if(ord(substr($str,$i,1))>0xa0)
{
if ($clen>=$start)
$tmpstr.=substr($str,$i,2);
$i++;
}
else
{
if ($ clen>=$start)
$tmpstr.=substr($str,$i,1);
}
}

return $tmpstr;
}
Function showShort($str,$len)
{
$tempstr = csubstr($str,0,$len);
if ($str<>$tempstr)
$tempstr .= " ..."; //What you want to end with, just modify it here.

return $tempstr;
}

------------- -------------------------------------------------- ------------------



6: Standardize your SQL statements


in front of tables and fields Add "`" so that errors will not occur due to misuse of keywords.
Of course I do not recommend you to use keywords.

For example
$Sql="INSERT INTO `xltxlm ` (`author`, `title`, `id`, `content`, `date`) VALUES ('xltxlm', 'use`', 1, 'criterion your sql string ', '2003-07-11 00: 00:00')"

"`"How to input? On the TAB key.


7: How to prevent the string in Html/PHP format from being interpreted, but as Display


PHP code as is:-------------------------------- -----------------------------------------------

$str="

PHP

";
Echo "Interpreted: ".$str."
Processed:";
Echo htmlentities(nl2br($str));
?>

-------------------------- -------------------------------------------------- ---



8: How to get the variable value outside the function in the function


PHP code:----------- -------------------------------------------------- ------------------

$a="PHP";
foo();
Function foo()
{
global $a;//Delete here and see what the result is
Echo "$a";
}
?>

-- -------------------------------------------------- ----------------------------



9: How do I know what functions the system supports by default?


PHP code:----------------------------------------- ------------------------------------------

< ?php
$arr = get_defined_functions();
Function php() {
}
echo "

"; 
Echo "Here shows all the functions supported by the system, and the custom function phpn";
print_r($arr); 
echo ""; 
?> 
---------------------------------------- --------------------------------------------------


10: How to compare the number of days between two dates


PHP code:-------------------------- -------------------------------------------------- ----

$Date_1="2003-7-15";//It can also be: $Date_1="2003-6-25 23:29:14"; 
$Date_2="1982-10-1";
$Date_List_1=explode("-",$Date_1);
$Date_List_2=explode("-",$Date_2);
$ d1=mktime(0,0,0,$Date_List_1[1],$Date_List_1[2],$Date_List_1[0]);
$d2=mktime(0,0,0,$Date_List_2[1],$ Date_List_2[2],$Date_List_2[0]);
$Days=round(($d1-$d2)/3600/24);
Echo "I have struggled for $Days days^_^"; 
?>

----------------------------------------- ------------------------------------------


11: Why after I upgraded PHP, the original program showed a full screen Notice: Undefined variable:


This is a warning, caused by the variable being undefined.
Open php.ini , find the error_reporting at the bottom, change it to error_reporting = E_ALL & ~E_NOTICE

For Parse error error
error_reporting(0) cannot be closed.
If you want to close any error prompts, open php.ini , find display_errors and set it to display_errors = Off. Any errors in the future will not be prompted.

Then what is error_reporting?



12: I want to report it at the beginning of each file , add a file at the end. But it is troublesome to add one by one 

1: Open the php.ini file 
 and set include_path= "c:"

2: Write two files 
auto_prepend_file.php and auto_append_file.php are saved in the c drive, and they will be automatically attached to the head and tail of each php file. 

3: Found in php.ini: 
Automatically add files before or after any PHP document. >
PHP code:---------------------------------------------- -------------------------------------

 Include "auto_prepend_file.php" ;

.....//Here is your program


Include "auto_append_file.php";
?>

------------------------------------------------ ----------------------------------




 13: How to use PHP to upload files 



PHP code: ---------------------------- -------------------------------------------------- --


 
 
 
Please select a file: 

< br>
 
 

 

$upload_file=$_FILES['upload_file']['tmp_name'];
$upload_file_name=$_FILES['upload_file']['name'];

if( $upload_file){
$file_size_max = 1000*1000;//1M limit file upload maximum capacity (bytes)
$store_dir = "d:/";// Storage location of uploaded files
$accept_overwrite = 1;//Whether overwriting the same file is allowed
//Check file size
if ($upload_file_size > $file_size_max) {
echo "Sorry, your file capacity is larger than specified";
exit; 
}

// Check read and write files
if (file_exists($store_dir . $upload_file_name) && !$accept_overwrite) {
Echo "A file with the same file name exists";
exit;
}

//Copy the file to the specified directory
if (!move_uploaded_file($upload_file,$store_dir.$upload_file_name)) {
echo "Failed to copy file";
exit;
}

}

Echo "
You uploaded a file:";
echo $_FILES['upload_file']['name'] ;
echo "
";
//The original name of the client machine file. 

Echo "The MIME type of the file is:";
echo $_FILES['upload_file']['type'];
//The MIME type of the file, the browser needs to provide this information Supported, such as "image/gif".
echo "
";

Echo "Upload file size:";
echo $_FILES['upload_file']['size'];
//Uploaded file The size, in bytes. 
echo "
";

Echo "The file is temporarily stored as:";
echo $_FILES['upload_file']['tmp_name'];
/ /The temporary file name stored on the server after the file is uploaded. 
echo "
";


$Erroe=$_FILES['upload_file']['error'];
switch($Erroe){
 case 0 :  Echo "upload successfully"; break; 
 case 1: 
 echo "uploaded files that exceed the value of upload_max_filesize options in php.ini."; Break; 
 case 2:  Echo "The size of the uploaded file exceeds the value specified by the MAX_FILE_SIZE option in the HTML form."; break;
 case 3:
 Echo "Only part of the file was uploaded"; break;
 case 4:
 Echo "No files uploaded";break;
}
?>

-------------------------- -------------------------------------------------- -------



14: How to configure the GD library


The following is my configuration process
1: Use dos command (also You can do it manually, copy all dll files in the dlls folder to the system32 directory) copy c:phpdlls*.dll c:windowssystem32 
2: Open php.ini
 and set extension_dir = "c:/php/extensions/ ";
3:
extension=php_gd2.dll; Remove the comma in front of extension. If there is no php_gd2.dll, the same is true for php_gd.dll. Make sure that this file does exist c:/php/extensions/php_gd2. dll
4: Run the following program for testing

PHP code:-------------------------------- -------------------------------------------------- 

Ob_end_flush();
//Note that no information can be output to the browser before this. Pay attention to whether auto_prepend_file is set.
header ("Content- type: image/png");
$im = @imagecreate (200, 100)
 or die ("Unable to create image");
$background_color = imagecolorallocate ($im, 0,0, 0 );
$text_color = imagecolorallocate ($im, 230, 140, 150);
imagestring ($im, 3, 30, 50, "A Simple Text String", $text_color);
imagepng ( $im);
?>

---------------------------------- --------------------------------------------------



Click here to view the results



15: What is UBB code


UBB code is a variant of HTML and is the Ultimate Bulletin Board (a foreign BBS program, also used in many places in China) uses a special TAG. 
 Even if the use of HTML is prohibited, you can still use UBBCode? to achieve it. Maybe you would rather use UBBCode? instead HTML, even if the forum allows the use of HTML, it is safer to use because it requires less code.

Q3boy’s UBB has examples, you can run the test directly


16: I want to modify MySQL user, password 

First of all, let me declare that in most cases, modifying MySQL requires root permissions in mysql, 
so ordinary users cannot change the password unless requesting the administrator.

Method 1
Use phpmyadmin, this is the simplest, modify the user table of the mysql library, 
But don’t forget to use the PASSWORD function. 

Method 2 
Use mysqladmin, which is a special case stated earlier. 
mysqladmin -u root -p password mypasswd 
After entering this command, you need to enter the original password of root, and then the root password will be changed to mypasswd. 
Change root in the command to your username, and you can change your own password. 
Of course, if your mysqladmin cannot connect to the mysql server, or you cannot execute mysqladmin, 
then this method is invalid. 
And mysqladmin cannot clear the password. 

The following methods are used at the mysql prompt and must have root permissions for mysql: 
Method 3
mysql> INSERT INTO mysql.user (Host,User,Password) 
 VALUES('%','jeffrey',PASSWORD('biscuit')); 
mysql> FLUSH PRIVILEGES 
To be exact, this is adding a user with the username jeffrey and the password biscuit. 
There is this example in the "mysql Chinese Reference Manual", so I wrote it out. 
Note that you need to use the PASSWORD function, and then use FLUSH PRIVILEGES. 

Method 4
Same as method 3, except that the REPLACE statement is used
mysql> REPLACE INTO mysql.user (Host,User,Password) 
VALUES('%','jeffrey ',PASSWORD('biscuit')); 
mysql> FLUSH PRIVILEGES 

Method 5 
Use the SET PASSWORD statement, 
mysql> SET PASSWORD FOR jeffrey@"%" = PASSWORD(' biscuit'); 
You must also use the PASSWORD() function, 
but there is no need to use FLUSH PRIVILEGES.

Method 6
Use GRANT... IDENTIFIED BY statement
mysql> GRANT USAGE ON *.* TO jeffrey@"%" IDENTIFIED BY 'biscuit'; 
Here is the PASSWORD() function is unnecessary, and there is no need to use FLUSH PRIVILEGES. 

Note: PASSWORD() [does not] perform password encryption in the same way as Unix password encryption. 


17: I want to know which website he connected to this page through



PHP code:------------ -------------------------------------------------- ------------------

//You must enter through a super connection to have output
Echo $_SERVER['HTTP_REFERER '];
?>

---------------------------------- ------------------------------------------------



18: What should you pay attention to when putting data into the database and taking it out to display on the page

When entering the database
$str=addslashes($str);
$sql=" insert into `tab` (`content`) values('$str')";
When leaving the library
$str=stripslashes($str);
When displaying
$str=htmlspecialchars( nl2br($str)) ; 





19: How to read the current address bar information



PHP code:- -------------------------------------------------- --------------------------

$s="http:// {$_SERVER['HTTP_HOST']}:{$_SERVER["SERVER_PORT"]}{$_SERVER['SCRIPT_NAME']}"; 
$se=''; 
foreach ($_GET as $key = > $value) { 
$se.=$key."=".$value."&"; 
} 
$se=Preg_Replace("/(.*)&$/", "$1",$se); 
$se?$se="?".$se:"";
echo $s."?$se"; 
?> 
- -------------------------------------------------- --------------------------




20: I clicked the back button , why the things you filled in before are missing

This is because you used session.
Solution:

PHP code:------------- -------------------------------------------------- ----------------

session_cache_limiter('private, must-revalidate');
session_start(); 
 .......
.....
?>

------------- -------------------------------------------------- ----------------



21: How to display the IP address in the picture


PHP code:- -------------------------------------------------- -----------------------------

 Header("Content-type: image/ png");
 $img = ImageCreate(180,50);
 $ip = $_SERVER['REMOTE_ADDR'];
 ImageColorTransparent($img,$bgcolor);
 $bgColor = ImageColorAllocate ($img, 0x2c,0x6D,0xAF); // Background color
 $shadow = ImageColorAllocate($img, 250,0,0); // Shadow color
 $textColor = ImageColorAllocate($img, oxff, oxff,oxff); // Font color
 ImageTTFText($img,10,0,78,30,$shadow,"d:/windows/fonts/Tahoma.ttf",$ip); //Display background
 ImageTTFText($img,10,0,25,28,$textColor,"d:/windows/fonts/Tahoma.ttf","your ip is".$ip); // Display IP
 ImagePng( $img);
 imagecreatefrompng($img);
 ImageDestroy($img);
?>

---------------- -------------------------------------------------- ---------------



22: How to get the user’s real IP


PHP code:---- -------------------------------------------------- --------------------------

function iptype1 () { 
if (getenv( "HTTP_CLIENT_IP")) { 
 return getenv("HTTP_CLIENT_IP"); 
} 
else { 
 return "none"; 
} 
} 
function iptype2 () { 
if (getenv("HTTP_X_FORWARDED_FOR")) { 
 return getenv("HTTP_X_FORWARDED_FOR"); 
} 
else { 
 return "none"; 
} 
} 
function iptype3 () { 
if (getenv("REMOTE_ADDR")) { 
 return getenv("REMOTE_ADDR"); 
} 
else { 
 return "none"; 
} 
} 
function ip() { 
$ip1 = iptype1(); 
 $ip2 = iptype2(); 
$ip3 = iptype3(); 
if (isset ($ip1) && $ip1 != "none" && $ip1 != "unknown") { 
 return $ip1; 
} 
elseif (isset($ip2) && $ip2 != "none " && $ip2 != "unknown") { 
 return $ip2; 
} 
elseif (isset($ip3) && $ip3 != "none" && $ip3 != "unknown") { 
 return $ip3; 
} 
 else { 
 return "none"; 
} 
} 

Echo ip(); 
?> 
------------------------------------------------ --------------------------------



23: How to read from the database Get all the records within three days

First of all, there must be a DATETIME field in the table to record the time, 
The format is '2003-7-15 16:50:00'

SELECT * FROM ` xltxlm` WHERE TO_DAYS(NOW()) - TO_DAYS(`date`) <= 3;


24: How to remotely connect to Mysql database 


 when adding users There is a host field in the mysql table, change it to "%", or specify the IP address that allows the connection, so that you can call it remotely.

$link=mysql_connect("192.168.1.80:3306","root","");


25: How to use regular expressions

Click here 
Special characters in regular expressions


26: After using Apache, the homepage appears garbled 


Method 1: 
AddDefaultCharset ISO-8859-1 Change AddDefaultCharset off 

Method 2: 
AddDefaultCharset GB2312
============================== ==========================
tip:
When you post the code, GB2312 will be interpreted as??????

If you change it to this, it won’t happen
                    
                     




http://www.bkjia.com/PHPjc/314770.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/314770.htmlTechArticleSummary of Php FAQ 1: Why can’t I get the variable? I POST data name from one web page to another web page , why can’t I get any value when outputting $name? In PHP4.2 and later versions, reg...