[php manual] exception handling

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Exception handling

PHP 5

Throw (throw) exception (exception) in the try code block and catch the exception in the catch code block

Each try must have at least one corresponding catch or finally block.

The object thrown must be an instance of the Exception class or a subclass of Exception, otherwise it will cause a PHP fatal error.

    try {      throw new Exception('异常提示语');      //throw 123;  //Fatal error: Uncaught Error: Can only throw objects 
      //throw new stdClass(); //Fatal error: Uncaught Error: Cannot throw objects that do not implement Throwable
    } catch (Exception $e) {      echo  $e->getMessage();
    }

catch

You can use multiple catch blocks to catch different categories of exceptions.
Normal execution (when no exception is thrown within the try block) will continue after the last catch block defined in sequence.
Exceptions can be thrown (or re-thrown) in catch blocks.

When an exception is thrown, the code following the statement will not be executed and PHP will try to find the first matching catch block.
If the exception is not caught, a PHP fatal error will be issued with the message "Uncaught Exception..." unless a handler is defined using set_exception_handler().

finally

In PHP 5.5 and higher, the finally block can also be specified after the catch block or instead of the catch block.
Regardless of whether an exception is thrown, the code in the finally block will always be executed after the try and catch blocks before normal execution resumes.

Example #4 Exception handling with a finally block(用finally块处理异常)<?phpfunction inverse($x) {
    if (!$x) {        throw new Exception(&#39;pision by zero.&#39;);
    }    return 1/$x;
}try {    echo inverse(5) . "\n";
} catch (Exception $e) {    echo &#39;Caught exception: &#39;,  $e->getMessage(), "\n";
} finally {    echo "First finally.\n";
}try {    echo inverse(0) . "\n";
} catch (Exception $e) {    echo &#39;Caught exception: &#39;,  $e->getMessage(), "\n";
} finally {    echo "Second finally.\n";
}// Continue executionecho "Hello World\n";?>

Example #5 Nested Exception (嵌套异常)<?phpclass MyException extends Exception { }class Test {
    public function testing() {
        try {            try {                throw new MyException(&#39;foo!&#39;);
            } catch (MyException $e) {                // rethrow it
                throw $e;
            }
        } catch (Exception $e) {
            var_dump($e->getMessage());
        }
    }
}$foo = new Test;$foo->testing();?>

Note 
set_exception_handler（）设置用户自定义的异常处理函数
Exception::getMessage 获取异常消息内容

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