PHP报错级别设置和原理分析

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原理简介

在PHP配置文件中php.ini有如下配置：

; Error Level Constants:
; E_ALL             - All errors and warnings (includes E_STRICT as of PHP 5.4.0)
; E_ERROR           - fatal run-time errors; E_RECOVERABLE_ERROR  - almost fatal run-time errors
; E_WARNING         - run-time warnings (non-fatal errors)
; E_PARSE           - compile-time parse errors
; E_NOTICE          - run-time notices (these are warnings which often result
;                     from a bug in your code, but it's possible that it was
;                     intentional (e.g., using an uninitialized variable and
;                     relying on the fact it is automatically initialized to an
;                     empty string); E_STRICT          - run-time notices, enable to have PHP suggest changes
;                     to your code which will ensure the best interoperability
;                     and forward compatibility of your code
; E_CORE_ERROR      - fatal errors that occur during PHP's initial startup
; E_CORE_WARNING    - warnings (non-fatal errors) that occur during PHP's
;                     initial startup; E_COMPILE_ERROR   - fatal compile-time errors
; E_COMPILE_WARNING - compile-time warnings (non-fatal errors)
; E_USER_ERROR      - user-generated error message
; E_USER_WARNING    - user-generated warning message
; E_USER_NOTICE     - user-generated notice message
; E_DEPRECATED      - warn about code that will not work in future versions
;                     of PHP
; E_USER_DEPRECATED - user-generated deprecation warnings;
; Common Values:
;   E_ALL (Show all errors, warnings and notices including coding standards.)
;   E_ALL & ~E_NOTICE  (Show all errors, except for notices)
;   E_ALL & ~E_NOTICE & ~E_STRICT  (Show all errors, except for notices and coding standards warnings.)
;   E_COMPILE_ERROR|E_RECOVERABLE_ERROR|E_ERROR|E_CORE_ERROR  (Show only errors)
; Default Value: E_ALL & ~E_NOTICE & ~E_STRICT & ~E_DEPRECATED
; Development Value: E_ALL
; Production Value: E_ALL & ~E_DEPRECATED & ~E_STRICT; http://php.net/error-reportingerror_reporting = E_ALL

上面配置中：error_reporting为设置配置级别；默认是E_ALL,意思显示所有Notice,Warning,Error信息(Show all errors, warnings and notices including coding standards.)。
在PHP手册预定义常量中有详细解释，下面为摘录的一部分：

例子:E_ALL & ~E_NOTICE
E_ALL: 111011111111111
E_NOTICE: 1000
~E_NOTICE: 0111
E_ALL & ~E_NOTICE：111011111110111

php就是这样通过二进制的转换来控制错误级别的。

调整错误级别

全局设置

更改php.ini文件中的error_reporting就可以达到效果。
例如：

1. error_reporting = E_ALL #输出所有错误，警告，notice信息
2. error_reporting = E_ALL & ~E_NOTICE #输出所有错误和警告信息，不输出notice信息
3. E_ALL & ~E_NOTICE & ~E_WARNING #输出所有错误信息,不输出警告，notice信息

局部设置

在脚本或程序中，通过ini_set()和error_reporting()设置可以达到效果。
例如:

ini_set("display_errors",1)
error_reporting(E_ALL)

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