异常处理try-catch-finally

时间:2021-05-01 16:18:15

php5.5新增 Finally模块

try {
    //好好干,出了问题不要怕,外面有人接应
} catch (HttpException $e) {
    //时刻准备着,处理上面抛出的HTTP问题
} catch (Exception $e) {
    //时刻准备着,处理他们都处理不了的问题
} finally {
    //打扫战场,都收拾好了再走人
}

try 中 return 后 finally 会继续执行,如果 finally 中也有return,则最终返回值为 finally 中 return 的值。
try 中 die 或 exit 后 finally 不会执行。

example01:

<?php
/**
finally块是个很好的设计,其中的return语句能覆盖其他块中的return语句,并处理try catch抛出的异常
无需try-catch嵌套来处理子try-catch抛出的异常
这个跟java的一样,c#是在finally块中存在return语句会抛出compile time error(编译时错误)
*/ function asdf()
{
try {
throw new Exception('error');
}
catch(Exception $e) {
echo "An error occurred";
throw $e;
}
finally {
//This overrides the exception as if it were never thrown
return "\nException erased";
}
} try {
echo asdf();
}
catch(Exception $e) {
echo "\nResult: " . $e->getMessage();
} /*
The output from above will look like this: An error occurred
Exception erased Without the return statement in the finally block it would look like this: An error occurred
Result: error
*/

example02:

<?php
/**
有个相悖的行为在PHP 5.5.3's finally 和 return statements:
在一个方法中,try块单返回一个变量,finally块修改这个变量,返回的是finally修改过的,
但当try块返回的变量参与运算(evaluated in-line),会忽略finally块对这个变量的修改
(不知道原因...)
*/
function returnVariable(){
$foo = 1;
try{
return $foo;
} finally {
$foo++;
}
} function returnVariablePlusZero(){
$foo = 1;
try{
return $foo+0;
} finally {
$foo++;
}
} $test1 = returnVariable(); // returns 2, not the correct value of 1.
$test2 = returnVariablePlusZero(); // returns correct value of 1, but inconsistent with $test1.

example03:

<?php
/**
小例子 验证变量
check if the name contains only letters, and does not contain the word name
*/ $name = "Name";
try
{
try
{
//preg_match() 返回 pattern 的匹配次数。 它的值将是0次(不匹配)或1次,因为 preg_match() 在第一次匹配后 将会停止搜索。 preg_match_all() 不同于此,它会一直搜索 subject 直到到达结尾。 如果发生错误 preg_match() 返回 FALSE 。
if(preg_match('/[^a-z]/i', $name))
{
throw new Exception("$name contains character other than a-z A-Z");
}
if(strpos(strtolower($name), 'name') !== false)
{
throw new Exception("$name contains the word name");
}
echo "The Name is valid";
}
catch (exception $e)
{
throw new Exception("insert name again", 0, $e);
}
} catch (exception $e)
{
if($e->getPrevious())
{
echo "The Previous Exception is: " . $e->getPrevious()->getMessage() . "<br/>";
}
echo "The Exception is: " . $e->getMessage() . "<br/>";
}

example04

<?php
/*
When catching an exception inside a namespace it is important that you escape to the global space:
如何逃离出命名空间
*/ namespace SomeNamespace; class SomeClass { function SomeFunction() {
try {
throw new Exception('Some Error Message');
} catch (\Exception $e) {
var_dump($e->getMessage());
}
} } //报错:
//Fatal error: Class 'SomeNamespace\Exception' not found in C:\xampp\htdocs\tonglei\index.php on line 8

example05

<?php

//下面的写法会报T_THROW Syntax Error.
someFunction() OR throw new Exception(); //这种写法可以用下面这个正确的形式
function throwException($message = null,$code = null) {
throw new Exception($message,$code);
} someFunction() OR throwException();