Summary of exception handling methods in php_PHP tutorial-PHP Tutorial-php.cn

Summary of exception handling methods in php. Friends in need can refer to this article.

When an exception is triggered, it usually happens:

An error exception handling module similar to other languages was added in PHP5. Exceptions generated in PHP code can be thrown by the throw statement and caught by the catch statement. Code that requires exception handling must be placed in a try code block to catch possible exceptions. Every try must have at least one corresponding catch. Use multiple catches to catch exceptions generated by different classes. When the try block no longer throws an exception or no catch is found that matches the thrown exception, the PHP code continues execution after jumping to the last catch. Of course, PHP allows exceptions to be thrown again within catch blocks. When an exception is thrown, the subsequent code will not continue to execute, and PHP will try to find the first matching catch. If an exception is not caught and is not handled accordingly using set_exception_handler(), PHP will generate a serious error and output an Uncaught Exception... (uncaught exception) message.

1. Hierarchical relationship of exception classes:

The code is as follows

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代码如下	复制代码
class NotFoundException extends Exception{} class InputException extends Exception{} class DBException extends Exception{}

class NotFoundException extends Exception{}
class InputException extends Exception{}
class DBException extends Exception{}

2. Configure the handler for uncaught exceptions:

代码如下	复制代码
function exception_uncaught_handler(Exception $e) { header('Content-type:text/html; charset=utf-8'); if ($e instanceof NotFoundException) exit($e->getMessage()); elseif ($e instanceof DBException) exit($e->getMessage()); else exit($e->getMessage()); } set_exception_handler('exception_uncaught_handler');

3. In the database connection code, manually throw DBException exception but If try...catch is not used for capture processing, the exception will be handled by PHP custom exception handler

代码如下

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exception_uncaught_handler()函数处理：

$this->resConn = mysql_connect ($CONFIGS['db_host'], $CONFIGS['db_user'], $CONFIGS['db_pwd']);
if (false == is_resource($this->resConn))
throw new DBException('数据库连接失败。'.mysql_error($this->resConn));

The code is as follows	Copy code
exception_uncaught_handler() function processing: $this->resConn = mysql_connect ( $CONFIGS['db_host'], $CONFIGS['db_user'], $CONFIGS['db_pwd']); if (false == is_resource($this->resConn)) throw new DBException('Database connection failed. '.mysql_error($this->resConn));

4. Business logic at a glance:

if (0 != strcmp($curAlbum->interest_id, $it))
throw new NotFoundException('Sorry, you visited The album does not exist');
The above is the specific use of PHP custom exception handler

Example

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The code is as follows

代码如下

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class customException extends Exception
{
public function errorMessage()
{
//error message
$errorMsg = 'Error on line '.$this->getLine().' in '.$this->getFile()
.': '.$this->getMessage().' is not a valid E-Mail address';
return $errorMsg;
}
}

$email = "someone@example.com";

try
{
//check if
if(filter_var($email, FILTER_VALIDATE_EMAIL) === FALSE)
{
//throw exception if email is not valid
throw new customException($email);
}
//check for "example" in mail address
if(strpos($email, "example") !== FALSE)
{
throw new Exception("$email is an example e-mail");
}
}

catch (customException $e)
{
echo $e->errorMessage();
}

catch(Exception $e)
{
echo $e->getMessage();
}
?>

class customException extends Exception<🎜>{<🎜>public function errorMessage()<🎜>{<🎜>//error message<🎜>$errorMsg = 'Error on line '.$this->getLine().' in ' .$this->getFile().': '.$this->getMessage().' is not a valid E-Mail address';return $errorMsg;}}$email = "someone@example.com";try { //check if if (filter_var($email, FILTER_VALIDATE_EMAIL) === FALSE) { //throw exception if email is not valid throw new customException($email); } //check for "example" in mail address if(strpos($email, "example") !== FALSE) { throw new Exception("$email is an example e-mail"); } }catch (customException $e) { echo $e->errorMessage(); }catch(Exception $ e) { echo $e->getMessage(); }?>

Explanation of the example:
The above code tests two conditions. If any condition is not true, an exception is thrown:

1. The customException() class is the old exception class Created by an extension of . This way it inherits all properties and methods of the old class.
2. Create errorMessage() function. If the e-mail address is not valid, this function returns an error message.
3. Execute the "try" code block, and no exception will be thrown under the first condition.
4. Since the e-mail contains the string "example", the second condition will trigger an exception.
5. The "catch" code block will catch the exception and display the appropriate error message
If the customException is not caught, the base exception is tightly caught, and the exception is handled there.

Rethrow the exception
Sometimes, when an exception is thrown, you may want to handle it differently than the standard way. The exception can be thrown again in a "catch" block.

The code is as follows

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/*
*/
/*
* Summary: There are three steps to use PHP exceptions:
* The first step: Define the exception class. If not defined, use the system default exception class;
* The second step: When When an exception occurs, use throw to throw an exception, such as ex1($num2); the parameter of the exception is $num2, which is obtained by the getMessage() of the exception;
* Step 3: Trigger the exception, use the try clause, when the conditions are met When throw new ex1($num);
* Step 4: catch exception catch (ex2 $e), which is equivalent to instantiating a defined exception class ex2 as $e;
*
* Note that multiple exceptions can be defined, but only one can be triggered, which means that only one exception can be captured with catch
*/
//================ Basic exception class
//Create a function that can throw an exception
function num($num){
if ($num>1){//Exception throwing condition
$msg=" The value cannot be greater than 1″;//Exception message
throw new Exception($msg);//Throw an exception
}
echo “The value is less than 1″;
}
// Trigger an exception in the "try" code block ){
echo "Error message:".$e->getMessage();//Exception() system method to obtain exception information
echo "Error file:".$e->getFile() ;//The system method of Exception() gets the exception file name
echo "Number of lines:".$e->getLine();//The system method of Exception() gets the exception line number
}
//================================================ =======================
echo “
================== ======================================
”;
//Extension Basic exception class
function checkEmail($email){//Define a function that can throw an exception to determine the validity of EMAIL
if (filter_var($email,FILTER_VALIDATE_EMAIL)==false){
throw new checkEmailException($email);//Throw an exception and use EMAIL as parameter
}
echo “Email is legal”;
}
class checkEmailException extends Exception{//Define extended exception class
public function errormsg(){
$msg="Error reason: ".$this->getMessage()." is not a legal EMAIL address! ”;
$msg.=”Error file name:”.$this->getFile();
$msg.=”Error line number:”.$this->getLine();
echo $msg;
}
}
$email=”email…..@chhua.com”;
try {//Trigger exception
checkEmail($email);
}
//Catch exception
catch (checkEmailException $e){
$e->errormsg();
}
//========== ========================Catching of multiple exceptions
echo “
============ =======================================
”;
class ex1 extends Exception{//Define an exception class
public function msg(){
$msg="Error reason: ".$this->getMessage()." is greater than 100
";
$msg.=”Error file:”.$this->getFile().”
”;
$msg.=”Error code:”.$this->getCode().”< ;br>”;
$msg.=”Number of lines:”.$this->getLine().”
”;
echo $msg;
}
}
class ex2 extends Exception{//Define an exception class
Public function msg(){
$msg="Error reason: ".$this->getMessage()." is equal to 100
" ;
$msg.=”Error file:”.$this->getFile().”
”;
$msg.=”Number of lines:”.$this->getLine( )."
";
echo $msg;
}
}
$num2=100;
try {
if ($num2>100){// Triggered when the condition is met
throw new ex1($num2);
}
if ($num2==100){//Triggered when the condition is met
throw new ex2($num2);
}
}
catch (ex2 $e){//Catch the triggered exception
$e->msg();
}
catch (ex1 $e){ //Capture the triggered exception
$e->msg();
}
/*
* Summary: There are three steps to use PHP exceptions:
* The first step: Define the exception class. If not defined, use the system default exception class;
* Step 2: When an exception occurs, use throw to throw an exception, such as ex1($num2); the parameter of the exception is $num2, which is obtained by getMessage() of the exception;
* Step 3: Trigger the exception, use try clause, when the conditions are met throw new ex1($num);
* Step 4: catch exception catch (ex2 $e), which is equivalent to instantiating a defined exception class ex2 as $e;
*
* Note that multiple exceptions can be defined, but only one can be triggered, which means that only one exception can be captured with catch
*/
?>