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>