php try catch throw 用法

1.try catch 捕捉不到fatal error致命错误

2.只有抛出异常才能被截获，如果异常抛出了却没有被捕捉到，就会产生一个fatal error

3.父类可以捕获子类抛出的异常

class ExceptionNew extends Exception{     
}
 
function try_throw($type) {
   if ($type == 1) {
        throw new ExceptionNew("sunyue");
   }
}
 
try {
     try_throw(1);
} catch (Exception $e) {
     echo $e->getMessage();
}

4.try中的代码一旦抛出异常，代码将停止运行，直接执行catch中的代码

5.多个catch捕获多个异常

PHP将查询一个匹配的catch代码块。如果有多个catch代码块，传递给每一个catch代码块的对象必须具有不同类型(或者可以用同一父类去捕获，这样只要一个catch就可以了)，这样PHP可以找到需要进入哪一个catch代码块。当try代码块不再抛出异常或者找不到catch能匹配所抛出的异常时，PHP代码就会在跳转最后一个catch的后面继续执行。因为原则4，所以每次其实这能抛出一个异常，一个异常被捕获。

class ExceptionNew extends Exception{      
}
class MyException extends Exception{      
}
function try_throw($type) {
    if ($type == 1) {
        throw new ExceptionNew("sun");
    }
    if($type > 0){
        throw new MyException("yue");
    }
}
try {
    try_throw(1);   
    try_throw(2);
}catch (ExceptionNew $e) {
    echo $e->getMessage();
    echo "----ExceptionNew";
}catch (MyException $e) {
    echo $e->getMessage();
    echo "----MyException";
}

上段代码执行结果：

sun----ExceptionNew

6. php7新增Throwable Interface

   To catch any exception in PHP 5.x and 7 with the same code, you would need to add a catch block for Exception AFTER catching Throwable first. Once PHP 5.x support is no longer needed, the block catching Exception can be removed.

    Virtually all errors in PHP 5 that were fatal, now throw instances of Error in PHP 7.

try {

   // Code that may throw an Exception or Error.

} catch (Throwable $t) {

   // Executed only in PHP 7, will not match in PHP 5

} catch (Exception $e) {

   // Executed only in PHP 5, will not be reached in PHP 7

}

参考链接：

• 5-new-features-php-7
• PHP 异常与错误 —— Throwable