Error summary PHP_PHP tutorial

Error summary PHP - constantly updated (must read for newbies)

Please enable all error prompts for development: error_reporting = E_ALL | E_STRICT

Blocking error prompts is equivalent to covering one’s ears and stealing the bell.

Write code in a standardized way and reduce errors by half.

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?

In PHP4.2 and later versions, 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);(note that there must be Session_Start() before extract($_SESSION)) at the front of the receiving web page.

Method 3: Read variables $a=$_GET["a"];$b=$_POST["b"], etc. one by one. Although this method is troublesome, it is safer.

2: Debug your program

You must know the value of a certain variable at runtime. This is what I did, create a file debug.php with the following content:

Ob_Start();

Session_Start();

　Echo ""; Echo "The _GET variables obtained on this page are:"; Print_R($_GET); Echo "The _POST variables obtained on this page are:"; Print_R($_POST); Echo "This page obtained The _COOKIE variables are: "; Print_R($_COOKIE); Echo "The _SESSION variables obtained on this page are: "; Print_R($_SESSION); Echo "";

Then set include_path = "c:/php" in php.ini and place debug.php in this folder,

In the future, you can include this file in every web page and view the obtained variable names and values.

　3: How to use session

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

It is very simple to pay for the session, such as:

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

　[php]

Session_start();

　$Name = "This is a Session example";

Session_Register("Name");//Note, do not write: Session_Register("$Name");

Echo $_SESSION["Name"];

//After that $_SESSION["Name"] is "This is a Session example"

　[/php]

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

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

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

　[php]

Session_Start();

　$_SESSION["name"]="value";

　[/php]

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

To cancel the session, you can do this:

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

　[php]

session_start();

session_unset();

session_destroy();

　[/php]

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

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 lines [php]

3 lines Session_Start();//There was already output in the first line before

4 lines .....

　5 lines [/php]

　==========================================

Tip 1:

Whenever ".....headers already sent.........." appears, it means that information is output to the browser before Session_Start().

Remove the output and it will be normal. (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:

　1 line [php] Ob_Start(); [/php]

　...Here is your program...

　2: What error is this

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, find session.save_path, and change it to session.save_path= "c:/tmp"

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

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

　[php]

$Var="hello php";//Change to $Var="hello php"; Try to get the result

　$post= "receive.php?Name=".$Var;

header("location:$post");

　[/php]

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

Contents of receive.php:

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

　[php]

Echo ""; Echo $_GET["Name"]; Echo "";

　[/php]

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

The correct method is:

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

　[php]

$Var="hello php";

　$post= "receive.php?Name=".urlencode($Var);

header("location:$post");

　[/php]

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

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

5: How to intercept Chinese characters of a specified length without ending with "[/php]", and replace the excess parts with "..."

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

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

　[php]

$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 .= "..."; //Whatever you want to end with, just modify it here.

return $tempstr;

　}

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

6: Standardize your SQL statements

Add "`" in front of the table and fields, so that errors will not occur due to misuse of keywords,

Of course I don’t 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 Html/PHP format string from being interpreted, but display it as it is

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

　[php]

$str="

PHP

　";

Echo "Explained: ".$str."

Processed: ";

Echo htmlentities(nl2br($str));

　[/php]

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

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

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

　[php]

$a="PHP";

foo();

Function foo()

　{

global $a;//Delete this and see what the result is

Echo "$a";

　}

　[/php]

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

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

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

　[php]

$arr = get_defined_functions();

Function php() {

　}

echo ""; Echo "This displays all the functions supported by the system, and the custom function phpn"; print_r($arr); echo "";

　[/php]

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

　10: How to compare the difference between two dates

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

　[php]

　$Date_1="2003-7-15";//It can also be:$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^_^";

　[/php]

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

　11: Why did the original program appear full screen after I upgraded PHP? Notice: Undefined variable:

This is a warning, caused by the variable being undefined.

Open php.ini, find error_reporting at the bottom, and change it to error_reporting = E_ALL & ~E_NOTICE

For Parse error

　error_reporting(0) cannot be closed.

If you want to turn off any error prompts, open php.ini, find display_errors, and set display_errors = Off. Any errors in the future will not be prompted.

So what is error_reporting?

　12: I want to add a file at the beginning and end of each file. But adding one by one is very troublesome

1: Open the php.ini file

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.

　auto_prepend_file = auto_prepend_file.php; attached to the head

auto_append_file = auto_append_file.php; attached to the end

From now on, each of your php files will be equivalent to

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

　[php]

　Include "auto_prepend_file.php" ;

　....//Here is your program

Include "auto_append_file.php";

　[/php]

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

　13: How to upload files using PHP

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

　[php]

Please select the file:

$upload_file=$_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 it is allowed to overwrite the same file

// Check file size

　if ($upload_file_size > $file_size_max) {

echo "Sorry, your file size 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, which requires the browser to provide support for this information, such as "image/gif".

echo "

　";

Echo "Upload file size:";

echo $_FILES['upload_file']['size'];

//The size of the uploaded file, in bytes.

echo "

　";

Echo "The file is temporarily stored as:" after uploading;

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 successful"; break;

Case 1:

Echo "The uploaded file exceeds the limit of the upload_max_filesize option 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;

　}

　[/php]

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

　14: How to configure the GD library

The following is my configuration process

1: Use dos command (you can also 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

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 this file does exist c:/php/extensions/php_gd2.dll

4: Run the following program to test

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

　[php]

Ob_end_flush();

// Note that no information can be output to the browser before this. Please 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);

　[/php]

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

　15: What is UBB code

UBB code is a variant of HTML and a special TAG used by Ultimate Bulletin Board (a foreign BBS program, which is also used in many places in China).

Even if the use of HTML is prohibited, you can still use UBBCode?. Maybe you prefer to use UBBCode? instead of HTML, even if the forum allows the use of HTML, because it uses less code and is safer.

There are examples in Q3boy’s UBB, you can run the test directly

16: I want to change the MySQL user and password

First of all, let me declare that in most cases, modifying MySQL requires root permissions in mysql,

So general users cannot change passwords unless requesting an administrator.

Method 1

Using phpmyadmin, this is the easiest, 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 password of root 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 all used at the mysql prompt and must have mysql root permissions:

Method 3

mysql> INSERT INTO mysql.user (Host,User,Password)

VALUES('%','jeffrey',PASSWORD('biscuit'));

mysql> FLUSH PRIVILEGES

To be precise, this is adding a user, the username is jeffrey and the password is biscuit.

There is this example in the "mysql Chinese Reference Manual", so I wrote it out.

Be careful to use the PASSWORD function, and then use FLUSH PRIVILEGES.

Method 4

Same as method three, except using the REPLACE statement

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';

　The PASSWORD() function is unnecessary here, 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:------------------------------------------------ ----------------------------------

　[php]

//You must enter through a super connection to have output

Echo $_SERVER['HTTP_REFERER'];

　[/php]

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

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

When put into storage

　$str=addslashes($str);

$sql="insert into `tab` (`content`) values('$str')";

When leaving the warehouse

　$str=stripslashes($str);

When displayed

　$str=htmlspecialchars(nl2br($str));

　19: How to read the current address bar information

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

　[php]

　$s="http://{$_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";

　[/php]

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

　20: I clicked the back button, why did the previously filled out information disappear?

This is because you used session.

Solution:

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

　[php]

session_cache_limiter('private, must-revalidate');

session_start();

　…………

　…………

　[/php]

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

　21: How to display IP address in pictures

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

　[php]

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);

　[/php]

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

　22: How to obtain the user’s real IP

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

　[php]

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();

　[/php]

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

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

First, 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

There is a host field in the mysql table for adding users, 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 changed to AddDefaultCharset off

Method 2:

AddDefaultCharset GB2312

================================================ =========

tip:

When you post the code, GB2312 will be interpreted as ??????

Change it to this and it won’t happen

　GB2312

　10: How to compare the number of days between two dates, (simpler algorithm)

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

　[php]

　$Date_1="2003-7-15";//It can also be:$Date_1="2003-7-15 23:29:14";

$Date_2="1982-10-1";

$d1=strtotime($Date_1);

$d2=strtotime($Date_2);

$Days=round(($d1-$d2)/3600/24);

Echo "I have struggled for $Days days^_^";

　[/php]

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

　27: Why do single quotes and double quotes become ('")

on the acceptance page?

Solution:

Method 1: Set: magic_quotes_gpc = Off in php.ini

Method 2: $str=stripcslashes($str)

28: How to keep the program running instead of stopping after 30 seconds

Set_time_limit(60)//The maximum running time is one minute

Set_time_limit(0)//Run until the program ends by itself, or stop manually

　29: Calculate the number of people currently online

Example 1: Using text to implement

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

　[php]

//First you must have permission to read and write files

//This program can be run directly. If an error is reported for the first time, it can be run later

　$online_log = "count.dat"; //File to save the number of people,

$timeout = 30; //If there is no action within 30 seconds, it will be considered offline

$entries = file($online_log);

　$temp = array();

　for ($i=0;$i

　$entry = explode(",",trim($entries[$i]));

　if (($entry[0] != getenv('REMOTE_ADDR')) && ($entry[1] > time())) {

array_push($temp,$entry[0].",".$entry[1]."n"); //Get other browsers’ information, remove the timeout ones, and save it in $temp

　}

　}

array_push($temp,getenv('REMOTE_ADDR').",".(time() + ($timeout))."n"); //Update the viewer's time

　$users_online = count($temp); //Calculate the number of people online

$entries = implode("",$temp);

//Write file

　$fp = fopen($online_log,"w");

　flock($fp,LOCK_EX); //flock() does not work properly in NFS and some other network file systems

fputs($fp,$entries);

flock($fp,LOCK_UN);

　fclose($fp);

echo "Currently there are".$users_online."People are online";

　[/php]

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

Example 2:

Use database to implement online users

　30: What is a template and how to use it

Here are several articles about templates

I use the phplib template

The following are the uses of several functions

　$T->Set_File("Definition as you like", "Template file.tpl");

　$T->Set_Block("defined in set_file"," ","define whatever you want");

　$T->Parse("defined in Set_Block"," ",true);

$T->Parse("Output the results as you like", "Defined in Set_File");

Set the loop format to:

How to generate a static web page from a template

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

　[php]

//Use phplib template here

　............

　............

　$tpl->parse("output","html");

　$output = $tpl->get("output");// $output is the entire web page content

Function wfile($file,$content,$mode='w') {

　$oldmask = umask(0);

$fp = fopen($file, $mode);

　if (!$fp) return false;

fwrite($fp,$content);

　fclose($fp);

umask($oldmask);

return true;

　}

// Write to file

Wfile($FILE,$output);

Header("location:$FILE");//Redirect to the generated web page

　}

　[/php]

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

phplib download address smarty download address

　31: How to use php to interpret characters

For example: input 2+2*(1+2), and automatically output 8

You can use the eval function

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

　[php]

$str=$_POST['str'];

eval("$o=$str;");

Echo "$o";

　[/php]

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

http://www.bkjia.com/PHPjc/764896.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/764896.htmlTechArticleError summary PHP - constantly updated (must read for novices) Please enable all error prompts when doing development: error_reporting = E_ALL | E_STRICT Blocking error messages is equivalent to covering one's ears and stealing the bell. Code is written in a standardized way with fewer errors...