Summary of PHP errors and exceptions

Error

Error level

Fatal Error: Fatal error (script terminates execution)

E_ERROR Fatal runtime fatal error, terminating program execution
E_CORE_ERROR PHP fatal error at startup
E_COMPILE_ERROR PHP compilation fatal error
E_USER_ERR OR Fatal errors generated by users

Parse Error: Parsing error during compilation (script terminates execution)

Parse Error Syntax parsing error during compilation

Warning Error: Warning error (only prompt information is given, but the script does not Terminate the run.)

E_WARNING Runtime warning (non-fatal error).
E_CORE_WARNING Warning (non-fatal error) that occurs during PHP initialization startup.
E_COMPILE_WARNING Compilation warning
E_USER_WARNING User-generated warning information

Notice Error: Notification error (only notification information is given, but the script will not terminate the run.)

E_NOTICE Runtime notification. Indicates that the script encounters a situation that may appear as an error.
E_USER_NOTICE Notification information generated by the user.

set_error_handler() captures errors [with limitations]

Function description

set_error_handler($callback);//Set a user function (error_handler) to handle errors that occur in the script.

Limitations of functions

The following levels of errors cannot be handled by user-defined functions: E_ERROR, E_PARSE, E_CORE_ERROR, E_CORE_WARNING, E_COMPILE_ERROR, E_COMPILE_WARNING, and most E_STRICTs generated in the file where the set_error_handler() function is called.

That is: set_error_handler($callback) can only capture some Warning and Notice level Errors generated by the system.

Usage

<?phpset_error_handler("error_handler");function error_handler($errno,$errstr,$errfile,$errline){    $str=<<<EOF         "errno":$errno
         "errstr":$errstr
         "errfile":$errfile
         "errline":$errlineEOF;
//获取到错误可以自己处理，比如记Log、报警等等    echo $str;
}echo $test;//$test未定义，会报一个notice级别的错误

Output result:

"errno":8"errstr":Undefined variable: test"errfile":/Users/shuchao/Desktop/handler.php"errline":13
如何捕获PHP的Fatal Error、Parse Error等

Requirement description

Get PHP's fatal error, such as recording it in the Log, which helps us analyze online problems and monitor online services.

Two functions

register_shutdown_function()

register_shutdown_function($callback)

register_shutdown_function(), put the function you want to register into [pretend to be a queue], wait until the script exits normally or displays the exit call , and then pull out the registered function for execution.

Three situations when register_shutdown_function() is called:

When the script exits normally;

When the script exits with an error (run-time not parse-time);

User When calling the exit method to exit.

error_get_last()

error_get_last();//The function gets the last error that occurred.

This function returns the last error that occurred in the form of an array.

The returned array contains 4 keys and values:

[type] - error type
[message] - error message
[file] - the file where the error occurred
[line] - the line where the error occurred

Use Method

<?php
register_shutdown_function( "fatal_handler" );
define(&#39;E_FATAL&#39;,  E_ERROR | E_USER_ERROR |  E_CORE_ERROR | 
        E_COMPILE_ERROR | E_RECOVERABLE_ERROR| E_PARSE );function fatal_handler() {  if( $error = error_get_last()) {    $errno   = $error["type"];    $errfile = $error["file"];    $errline = $error["line"];    $errstr  = $error["message"];    $str=<<<EOF         "errno":$errno
         "errstr":$errstr
         "errfile":$errfile
         "errline":$errlineEOF;
//获取到错误可以自己处理，比如记Log、报警等等    echo $str;
  }
}

Strongly note

that the register_shutdown_function() function will not be called when parse-time error occurs. Register_shutdown_function() will be called only when a run-time error occurs.

Let’s give an example below:

NO.1

error_handler.php

<?phpregister_shutdown_function("error_handler");function error_handler(){    echo "Yeah,it&#39;s worked!";
}function test(){}function test(){}

The execution results are as follows:

Fatal error: Cannot redeclare test() (previously declared in /Users/shuchao/Desktop/error_handler.php:6 ) in/Users/shuchao/Desktop/error_handler.php on line 7

Cause analysis

When executing error_handler.php, due to the repeated definition of two functions test(), an error occurred in the parse-time of php (not run-time), so the function in register_shutdown_function() cannot be called back.

NO.2

error_handler.php

<?phpregister_shutdown_function("error_handler");function error_handler(){    echo "Yeah,it&#39;s worked!";
}if(true){   function test(){}
}function test(){}

The execution results are as follows:

Fatal error: Cannot redeclare test() (previously declared in /Users/shuchao/Desktop/error_handler.php:9) in /Users/shuchao/Desktop/error_handler.php on line 7Yeah,it's worked!%

Cause analysis

我们看到，上面回调了register_shutdown_function().
因为我们加了一个if()判断，if()里面的test()方法，相当于一个闭包，与外面的test()名称不冲突。
也就是，上面的代码在parse-time没有出错，而是在run-time的时候出错了，所以我们能够获取到fatal error。

NO.3

error_handler.php

<?phpregister_shutdown_function("error_handler");function error_handler(){    echo "Yeah,it&#39;s worked!";}
test_error.php
<?phpinclude &#39;./error_handler.php&#39;;function test(){}function test(){}

执行 test_error.php的结果如下

Fatal error: Cannot redeclare test() (previously declared in /Users/shuchao/Desktop/test_error.php:3) in/Users/shuchao/Desktop/test_error.php on line 4

原因分析

当我们在运行test_error.php的时候,因为redeclare了两个test()方法，所以php的语法解析器在parse-time的时候就出错了。 所以不能回调register_shutdown_function()中的方法，不能catch住这个fatal error。

NO.4

error_handler.php
<?phpregister_shutdown_function("error_handler");function error_handler(){    echo "Yeah,it&#39;s worked!";}
test_error.php
<?phpfunction test(){}function test(){}
include_all.php
require &#39;./error_handler.php&#39;;require &#39;./test_error.php&#39;;

执行 include_all.php的结果如下

Fatal error: Cannot redeclare test() (previously declared in /Users/shuchao/Desktop/include_all.php:2) in /Users/shuchao/Desktop/include_all.php on line 3Yeah,it's worked!%

结果分析

上面我们捕获了fatal_error.因为在运行include_all.php的时候，include_all.php本身语法并没有出错，也就是在parse-time的时候并没有出错，而是include的文件出错了，也就是在run-time的时候出错了，这个时候是能回调register_shutdown_function()中的函数的。

强烈建议：如果我们要使用register_shutdown_function进行错误捕捉，使用NO.4，最后一种方法，可以确保错误都能捕捉到。

更优美的写法·获取所有错误

set_error_handler()与register_shutdown_function()、error_get_last()的结合使用
<?phpregister_shutdown_function( "fatal_handler" );set_error_handler("error_handler");define(&#39;E_FATAL&#39;,  E_ERROR | E_USER_ERROR |  E_CORE_ERROR |         E_COMPILE_ERROR | E_RECOVERABLE_ERROR| E_PARSE );//获取fatal errorfunction fatal_handler() {    $error = error_get_last();    if($error && ($error["type"]===($error["type"] & E_FATAL))) {        $errno   = $error["type"];        $errfile = $error["file"];        $errline = $error["line"];        $errstr  = $error["message"];        error_handler($errno,$errstr,$errfile,$errline);  }}//获取所有的errorfunction error_handler($errno,$errstr,$errfile,$errline){    $str=<<<EOF         "errno":$errno         "errstr":$errstr         "errfile":$errfile         "errline":$errlineEOF;//获取到错误可以自己处理，比如记Log、报警等等    echo $str;}
Exception
Exception与Error的区别
Exception

当异常抛出的时候，我们是想要去捕获他，并去做处理的。所以异常经常被当做程序的控制流程使用。

Error

Error是不可恢复的，是在开发过程中要去解决的。

使用Exception的例子

我想执行insert语句插入一条数据，可能插入失败(比如ID重复)，注意是可能失败，所以这是一个可能的情况，也就是异常情况。我们就可以使用异常来处理这个问题

try {  $row->insert();  $inserted = true;
} catch (Exception $e) {  echo "There was an error inserting the row - ".$e->getMessage();  $inserted = false;
}echo "Some more stuff";

如何catch一个未捕获的Exception

场景描述

假设程序中的有些地方直接throw了异常，没有进行catch。我们现在想要不管在程序的任何一个地方throw异常，即便在throw的地方没有被catch，我们也要能catch住，如何做到呢？

一个函数:set_exception_handler()

//设置默认的异常处理程序，用于没有用 try/catch 块来捕获的异常。 在 exception_handler 调用后异常会中止。

set_exception_handler()

使用示例

1、exception_handler.php
<?phpset_exception_handler("my_exception");function my_exception($exception){    echo $exception->getMessage();}
2、test_exception.php
<?phprequire "./exception_handler.php";throw new Exception("I am Exception");

现在我们运行 test_exception.php，结果如下：

I am Exception //证明我们throw的Exception被捕获了