Analysis of PHP5 exception handling using instances _ PHP Tutorial

Analyze the PHP5 exception handling using an instance. <? Php *** ■ (I) PHP5 exception handling ** PHP5 adds an exception handling module similar to other languages. Exceptions in PHP code can be thrown by the throw * statement and caught. <? Php
/**
* ■ (I) PHP5 exception handling
*
* PHP 5 adds an exception handling module similar to other languages. Exceptions generated in PHP code can be throw
* The statement is thrown and captured by the catch statement. All codes that require exception handling must be placed in the try code block
* Detects possible exceptions. Each try must have at least one catch corresponding to it. Use multiple catch
* Exceptions generated by different classes can be captured. When the try code block does not throw an exception or the catch cannot be found
* When an exception is thrown, the PHP code will continue to be executed after the jump to the last catch. Of course, PHP
* Throw can be thrown again in the catch code block.
* When an exception is thrown, the code after the exception (note: refers to the code block in which the exception is thrown) will not continue.
* Execute, and PHP will try to find the first catch that can match it. If an exception is not caught
* If set_exception_handler () is useless, PHP will generate
* Serious errors, and the output of the Uncaught Exception... (no Exception is captured) prompt information.
*/
?>
<? Php
/**
* Exception. php
*
* ■ (II) attributes and methods of the PHP 5 built-in exception classes
* The following code only describes the structure of the built-in exception handling class. it is not a practical usable code.
*/

Class Exception {
Protected $ message = 'unknown exception'; // exception information
Protected $ code = 0; // custom exception code
Protected $ file; // file name with an exception
Protected $ line; // The code line number with an exception

Function _ construct ($ message = null, $ code = 0 );
Final function getMessage (); // returns exception information
Final function getCode (); // return the exception code (code)
Final function getFile (); // returns the file name with an exception
Final function getLine (); // return the code line number in which an exception occurs.
Final function getTrace (); // backtrace () array
Final function getTraceAsString (); // getTrace () information formatted as a string

Reload method
Function _ toString (); // output string
}

?>

<? Php
/**
* Syntax. php
*/

// ■ (3) syntax structure and analysis

// PHP has two formats for throwing an exception:

// [1] try... catch...
Try {
// Perform operations that may be abnormal, such as database errors and file errors
} Catch (Exception $ e ){
// Print the error message
}

// [2] throw
$ Message = 'I must be run in the try {} block. if an exception occurs, I ($ message) will be returned (passed) to catch () for example, the above $ e ';
$ Code = 123; // error code number. you can use $ e-> getCode () in the catch block to return my value 123, so that I can customize the error code number.

Throw new Exception ($ message, $ code );

// Note that PHP exception handling does not throws

?>

<? Php
/**
* Example. php
*/
// ■ (4) two instances master PHP exception handling


// Example [1] use try... catch
/* PDO connects to the mysql database. if you have not read the PDO, first check the PDO constructor. otherwise, skip example 1 and see Example 2 */
$ Dsn = 'MySQL: host = localhost; dbname = testdb ';
$ User = 'dbuser ';
$ Password = 'dbpass ';

Try {
$ Dbh = new PDO ($ dsn, $ user, $ password); // An exception may occur when you create a database connection object.
Echo 'If an exception occurs above, I cannot be displayed ';
} Catch (PDOException $ e ){
Echo 'connection failed: '. $ e->__ toString ();
}
?>

<? Php
// Example [2] try... cathc and throw
Try {
$ Error = 'I throw exception information and exit the try block ';
If (is_dir ('./tests ')){
Echo 'Do something .';
} Else {
Throw new Exception ($ error, 12345 );
}
Echo 'if there is an exception above, it won't turn to me !~ <Br/> ', "n ";
} Catch (Exception $ e ){
Echo 'capture exception: ', $ e-> getMessage (), $ e-> getCode (), "n <br/>"; // Display $ error and 123456
}
Echo 'continue execution ';
?>

<? Php
// PHP processing is easier to learn than JAVA, because JAVA has too many exception classes and throws.
?>

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