PHP error mechanism knowledge summary, PHP mechanism summary_PHP tutorial

A summary of PHP error mechanism knowledge, a summary of PHP mechanism

The error mechanism of PHP is also very complicated. I have been working in PHP for several years and have not summarized it carefully. I will make up for it now. A lesson.

Special note: The PHP version of this article uses 5.5.32

PHP error level

First of all, you need to understand what errors there are in php. As of php5.5, there are a total of 16 error levels

Note: Please make sure to turn on error_log:
when trying the code below

error_reporting(E_ALL);
ini_set('display_errors', 'On'); 

E_ERROR

This error is a fatal error and will display Fatal Error on the page. When this error occurs, the program cannot continue to execute

Error example:

// Fatal error: Call to undefined function hpinfo() in /tmp/php/index.php on line 5
hpinfo(); //E_ERROR 

Note that if there is an uncaught exception, this level will also be triggered.

// Fatal error: Uncaught exception 'Exception' with message 'test exception' in /tmp/php/index.php:5 Stack trace: #0 {main} thrown in /tmp/php/index.php on line 5
throw new \Exception("test exception"); 

E_WARNING

This error is just a warning and will not terminate the script. The program will continue and the error message displayed is Warning. For example, include a file that does not exist.

//Warning: include(a.php): failed to open stream: No such file or directory in /tmp/php/index.php on line 7
//Warning: include(): Failed opening 'a.php' for inclusion (include_path='.:/usr/share/pear:/usr/share/php') in /tmp/php/index.php on line 7
include("a.php"); //E_WARNING 

E_NOTICE

This kind of error is more minor and reminds you that this place should not be written like this. This is also a runtime error. The wrong code may not have problems elsewhere, but only in the current context.

For example, the $b variable does not exist, we assign it to another variable

//Notice: Undefined variable: b in /tmp/php/index.php on line 9
$a = $b; //E_NOTICE 

E_PARSE

This error occurs during compilation. A syntax error is found during compilation and syntax analysis cannot be performed.

For example, z below is not set as a variable.

// Parse error: syntax error, unexpected '=' in /tmp/php/index.php on line 20
z=1; // E_PARSE 

E_STRICT

This error was introduced after PHP5. Your code can run, but it is not the way PHP recommends writing it.

For example, when passing function parameter symbol

// Strict Standards: Only variables should be passed by reference in /tmp/php/index.php on line 17
function change (&$var) {
$var += 10;
}
$var = 1;
change(++$var);
// E_STRICT 

E_RECOVERABLE_ERROR

This level is actually ERROR level, but it is expected to be captured. If it is not captured by error processing, the performance is the same as E_ERROR.

It often occurs when the formal parameter defines a type, but the wrong type is passed in when calling. Its error reminder also has the word Catachable in front of E_ERROR's fatal error.

//Catchable fatal error: Argument 1 passed to testCall() must be an instance of A, instance of B given, called in /tmp/php/index.php on line 37 and defined in /tmp/php/index.php on line 33
class A {
}
class B {
}
function testCall(A $a) {
}
$b = new B();
testCall($b); 

E_DEPRECATED

This error means that you are using an old version of the function, and later versions of this function may be disabled or not maintained.

For example, curl’s CURLOPT_POSTFIELDS uses @FILENAME to upload files

// Deprecated: curl_setopt(): The usage of the @filename API for file uploading is deprecated. Please use the CURLFile class instead in /tmp/php/index.php on line 42
$ch = curl_init("http://www.remotesite.com/upload.php");
curl_setopt($ch, CURLOPT_POSTFIELDS, array('fileupload' => '@'. "test")); 

E_CORE_ERROR, E_CORE_WARNING

These two errors are generated by the PHP engine and occur during the PHP initialization process.

E_COMPILE_ERROR, E_COMPILE_WARNING

These two errors are generated by the PHP engine and occur during the compilation process.

E_USER_ERROR, E_USER_WARNING, E_USER_NOTICE, E_USER_DEPRECATED,

These errors are all created by users. Using trigger_error is equivalent to an opening to trigger various error types for users. This is a good way to escape try catch exceptions.

trigger_error("Cannot divide by zero", E_USER_ERROR);
// E_USER_ERROR
// E_USER_WARING
// E_USER_NOTICE
// E_USER_DEPRECATED 

E_ALL

All error and warning messages when E_STRICT is out.

Error Control

There are many configurations and parameters in php that can control errors and error log display. The first step, what we need to know is what are the incorrect configurations in PHP?

According to the php php-fpm model, there are actually two configuration files that will affect the display of php errors. One is the configuration file php.ini of php itself, and the other is the configuration file of php-fpm. php -fpm.conf.

Configuration in php.ini

error_reporting = E_ALL // 报告错误级别，什么级别的
error_log = /tmp/php_errors.log // php中的错误显示的日志位置
display_errors = On // 是否把错误展示在输出上，这个输出可能是页面，也可能是stdout
display_startup_errors = On // 是否把启动过程的错误信息显示在页面上，记得上面说的有几个Core类型的错误是启动时候发生的，这个就是控制这些错误是否显示页面的。
log_errors = On // 是否要记录错误日志
log_errors_max_len = 1024 // 错误日志的最大长度
ignore_repeated_errors = Off // 是否忽略重复的错误
track_errors = Off // 是否使用全局变量$php_errormsg来记录最后一个错误
xmlrpc_errors = 0 //是否使用XML-RPC的错误信息格式记录错误
xmlrpc_error_number = 0 // 用作 XML-RPC faultCode 元素的值。
html_errors = On // 是否把输出中的函数等信息变为HTML链接
docref_root = http://manual/en/ // 如果html_errors开启了，这个链接的根路径是什么
fastcgi.logging = 0 // 是否把php错误抛出到fastcgi中 

We are often asked, what is the difference between error_reporting and display_errors? These two functions are completely different.

PHP will log and standard output by default (if it is fpm mode, the standard output is the page)

The parameter of error_reporting is the error level. Indicates what level should trigger an error. If we tell PHP that all error levels do not need to trigger errors, then neither the log nor the page will display this error, which is equivalent to nothing happening.

display_errors controls whether error messages should be displayed on standard output

log_errors controls whether error information should be recorded in the log.

error_log is the location where the error log is displayed. This is often rewritten in php-fpm, so it is often found that the error logs of cli and fpm are not in the same file.

The ignore_repeated_errors flag controls that if there are duplicate logs, only one will be recorded, such as the following program:

error_reporting(E_ALL);
ini_set('ignore_repeated_errors', 1);
ini_set('ignore_repeated_source', 1);

$a = $c; $a = $c; //E_NOTICE
//Notice: Undefined variable: c in /tmp/php/index.php on line 20 

NOTICE would have appeared twice, but now, it will only appear once...

track_errors开启会把最后一个错误信息存储到变量里面去，这个可能在对记日志的时候会有一些用处吧。不过我觉得真是没啥用...

html_errors 和 docref_root 两个是个挺有人性化的配置，配置了这两个参数以后，我们返回的错误信息中如果有一些在文档中有的信息，就会变成链接形式。

error_reporting(E_ALL);
ini_set('html_errors', 1);
ini_set('docref_root', "https://secure.php.net/manual/zh/");
include("a2.php"); //E_WARNING 

页面显示：

能让你快速定位到我们出现错误的地方。是不是很人性～

php-fpm中的配置

error_log = /var/log/php-fpm/error.log // php-fpm自身的日志
log_level = notice // php-fpm自身的日志记录级别
php_flag[display_errors] = off // 覆盖php.ini中的某个配置变量，可被程序中的ini_set覆盖
php_value[display_errors] = off // 同php_flag
php_admin_value[error_log] = /tmp/www-error.log // 覆盖php.ini中的某个配置变量，不可被程序中的ini_set覆盖
php_admin_flag[log_errors] = on // 同php_admin_value
catch_workers_output = yes // 是否抓取fpmworker的输出
request_slowlog_timeout = 0 // 慢日志时长
slowlog = /var/log/php-fpm/www-slow.log // 慢日志记录 

php-fpm的配置中也有一个error_log配置，这个很经常会和php.ini中的error_log配置弄混。但他们记录的东西是不一样的，

php-fpm的error_log只记录php-fpm本身的日志，比如fpm启动，关闭。

而php.ini中的error_log是记录php程序本身的错误日志。

那么在php-fpm中要覆盖php.ini中的error_log配置，就需要使用到下面几个函数：

•php_flag
•php_value
•php_admin_flag
•php_admin_value

这四个函数admin的两个函数说明这个变量设置完之后，不能在代码中使用ini_set把这个变量重新赋值了。而php_flag/value就仍然以php代码中的ini_set为准。

slowlog是fpm记录的，可以使用request_slowlog_timeout设置判断慢日志的时长。

总结

我们经常弄混的就是日志问题，以及某些级别的日志为何没有记录到日志中。最主要的是要看error_log，display_errors, log_errors这三个配置，只是在看配置的时候，我们还要注意区分php.ini里面的配置是什么，php-fpm.ini里面的配置是什么。

好吧，我觉得弄懂这些配置，基本就没有php日志记录不了的WTF的问题了。

关于PHP错误机制知识汇总小编就给大家介绍到这里，希望对大家有所帮助！

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