An example analysis of PHP5 exception handling _php Tutorial

<?php
/**
* Exception Handling for ㈠PHP5
*
* PHP 5 Adds an exception handling module similar to other languages. Exceptions generated in PHP code can be thrown
* Statements are thrown and captured by catch statements. The code that requires exception handling must be placed inside a try code block to
* Catches a possible exception. Each try must have at least one catch corresponding to it. Using multiple catch
* You can capture exceptions that are generated by different classes. When a try code block no longer throws an exception or cannot find a catch to match
* When the exception is thrown, the PHP code will continue to execute after jumping to the last catch. Of course, PHP
* Allows the throw (throw) exception to be thrown again within the catch code block.
* When an exception is thrown, the code behind it (the code block where the exception was thrown) will not continue
* Executes, and PHP tries to find the first catch to match. If an exception is not captured, and
* And without using Set_exception_handler () for the appropriate processing, then PHP will produce a
* A serious error, and output uncaught Exception ... (The exception is not caught) prompt information.
*/
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<?php
/**
* exception.php
*
* ㈡PHP5 properties and methods of the built-in exception classes
* The following code is only for the purpose of explaining the structure of the built-in exception-handling class, which is not a meaningful piece of code available.
*/

Class exception{
protected $message = ' Unknown exception '; Exception information
protected $code = 0; User-defined exception codes
protected $file; The file name of the exception that occurred
protected $line; The line number of the code where the exception occurred

function __construct ($message = null, $code = 0);
Final function getMessage (); Return exception information
Final function GetCode (); Return exception code (codename)
Final function getFile (); Returns the file name of the exception that occurred
Final function getLine (); Returns the line number of the code where the exception occurred
Final function gettrace (); BackTrace () array
Final function gettraceasstring (); Gettrace () information that has been rasterized into a string

Methods that can be overloaded
function __tostring (); A string that can be output
}

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/**
* Syntax. php
*/

㈢ Grammatical structure and analysis

PHP has two types of exception-throwing formats, as follows

"1" Try...catch ...
try {
Implement operations that may be abnormal, such as database errors, file errors
}catch (Exception $e) {
Print error message
}

"2" throw
$message = ' I must be running in the try{} block, I ($message) will be returned (passed) to an instance of the exception object in the catch () such as the above $e ';
$code = 123; The error code number, which can be $e->getcode () in the Catch block, returns my value of 123 so that I can customize the error code number

throw new Exception ($message, $code);

Learn Java Note that PHP exception handling does not throws

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/**
* example.php
*/
㈣ Two examples of PHP exception handling


Example "1" with Try...catch
/* PDO connect to MySQL database, if you have not seen PDO, first look at the PDO constructor, or skip example 1 to see Example 2 */
$dsn = ' Mysql:host=localhost;dbname=testdb ';
$user = ' Dbuser ';
$password = ' Dbpass ';

try {
$DBH = new PDO ($DSN, $user, $password); Creating database connection objects is prone to exceptions
Echo ' If there is an exception above it will not show me ';
} catch (Pdoexception $e) {
Echo ' Connection failed: '. $e->__tostring ();
}
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example [2] Try: CATHC and throw together
try {
$error = ' I throw an exception message and jump out of the try Block ';
if (Is_dir ('./tests ')) {
Echo ' do sth. ';
}else{
throw new Exception ($error, 12345);
}
Echo ' There's something wrong with it, it's not my turn! ~
', "n";
} catch (Exception $e) {
Echo ' catch exception: ', $e->getmessage (), $e->getcode (), "N
"; Show $error and 123456
}
Echo ' continues to execute ';
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PHP's processing is much easier to learn than Java, because Java has too many exceptions, throws, etc.
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