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 $e) {
//时刻准备着，处理他们都处理不了的问题
} finally {
//打扫战场，都收拾好了再走人
}
try 中 return 后 finally 会继续执行，如果 finally 中也有return，则最终返回值为 finally 中 return 的值。
try 中 die 或 exit 后 finally 不会执行。
example01:
<?<span>php
</span><span>/*</span><span>*
finally块是个很好的设计，其中的return语句能覆盖其他块中的return语句，并处理try catch抛出的异常
无需try-catch嵌套来处理子try-catch抛出的异常
这个跟java的一样，c#是在finally块中存在return语句会抛出compile time error（编译时错误）
</span><span>*/</span>
<span>function</span><span> asdf()
{
</span><span>try</span><span> {
</span><span>throw</span> <span>new</span> <span>Exception</span>('error'<span>);
}
</span><span>catch</span>(<span>Exception</span> <span>$e</span><span>) {
</span><span>echo</span> "An error occurred"<span>;
</span><span>throw</span> <span>$e</span><span>;
}
finally {
</span><span>//</span><span>This overrides the exception as if it were never thrown</span>
<span>return</span> "\nException erased"<span>;
}
}
</span><span>try</span><span> {
</span><span>echo</span><span> asdf();
}
</span><span>catch</span>(<span>Exception</span> <span>$e</span><span>) {
</span><span>echo</span> "\nResult: " . <span>$e</span>-><span>getMessage();
}
</span><span>/*</span><span>
The output from above will look like this:
An error occurred
Exception erased
Without the return statement in the finally block it would look like this:
An error occurred
Result: error
</span><span>*/</span>
example02:
<?<span>php
</span><span>/*</span><span>*
有个相悖的行为在PHP 5.5.3's finally 和 return statements：
在一个方法中，try块单返回一个变量，finally块修改这个变量，返回的是finally修改过的，
但当try块返回的变量参与运算（evaluated in-line），会忽略finally块对这个变量的修改
（不知道原因...）
</span><span>*/</span>
<span>function</span><span> returnVariable(){
</span><span>$foo</span> = 1<span>;
</span><span>try</span><span>{
</span><span>return</span> <span>$foo</span><span>;
} finally {
</span><span>$foo</span>++<span>;
}
}
</span><span>function</span><span> returnVariablePlusZero(){
</span><span>$foo</span> = 1<span>;
</span><span>try</span><span>{
</span><span>return</span> <span>$foo</span>+0<span>;
} finally {
</span><span>$foo</span>++<span>;
}
}
</span><span>$test1</span> = returnVariable(); <span>//</span><span> returns 2, not the correct value of 1.</span>
<span>$test2</span> = returnVariablePlusZero(); <span>//</span><span> returns correct value of 1, but inconsistent with $test1.</span>
example03:
<?<span>php
</span><span>/*</span><span>*
小例子 验证变量
check if the name contains only letters, and does not contain the word name
</span><span>*/</span>
<span>$name</span> = "Name"<span>;
</span><span>try</span><span>
{
</span><span>try</span><span>
{
</span><span>//</span><span>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 。</span>
<span>if</span>(<span>preg_match</span>('/[^a-z]/i', <span>$name</span><span>))
{
</span><span>throw</span> <span>new</span> <span>Exception</span>("<span>$name</span> contains character other than a-z A-Z"<span>);
}
</span><span>if</span>(<span>strpos</span>(<span>strtolower</span>(<span>$name</span>), 'name') !== <span>false</span><span>)
{
</span><span>throw</span> <span>new</span> <span>Exception</span>("<span>$name</span> contains the word name"<span>);
}
</span><span>echo</span> "The Name is valid"<span>;
}
</span><span>catch</span> (<span>exception</span> <span>$e</span><span>)
{
</span><span>throw</span> <span>new</span> <span>Exception</span>("insert name again", 0, <span>$e</span><span>);
}
}
</span><span>catch</span> (<span>exception</span> <span>$e</span><span>)
{
</span><span>if</span>(<span>$e</span>-><span>getPrevious())
{
</span><span>echo</span> "The Previous Exception is: " . <span>$e</span>->getPrevious()->getMessage() . "<br/>"<span>;
}
</span><span>echo</span> "The Exception is: " . <span>$e</span>->getMessage() . "<br/>"<span>;
}</span>
example04
<?<span>php
</span><span>/*</span><span>
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
</span><span>*/</span><span>
namespace SomeNamespace;
</span><span>class</span><span> SomeClass {
</span><span>function</span><span> SomeFunction() {
</span><span>try</span><span> {
</span><span>throw</span> <span>new</span> <span>Exception</span>('Some Error Message'<span>);
} </span><span>catch</span> (\<span>Exception</span> <span>$e</span><span>) {
</span><span>var_dump</span>(<span>$e</span>-><span>getMessage());
}
}
}
</span><span>//</span><span>报错：
//Fatal error: Class 'SomeNamespace\Exception' not found in C:\xampp\htdocs\tonglei\index.php on line 8</span>
example05
<?<span>php
</span><span>//</span><span>下面的写法会报T_THROW Syntax Error.</span>
someFunction() OR <span>throw</span> <span>new</span> <span>Exception</span><span>();
</span><span>//</span><span>这种写法可以用下面这个正确的形式</span>
<span>function</span> throwException(<span>$message</span> = <span>null</span>,<span>$code</span> = <span>null</span><span>) {
</span><span>throw</span> <span>new</span> <span>Exception</span>(<span>$message</span>,<span>$code</span><span>);
}
someFunction() OR throwException();<br /><br /></span>
