Errors and Exceptions in PHP

Errors and exceptions are two completely different concepts

Errors

Error types

A total of 16

Values	Constant	Description	Remarks
1	E_ERROR (integer)	Fatal runtime error. This type of error is generally an unrecoverable situation, such as a problem caused by memory allocation. The consequence is that the script terminates and does not continue to run.
2	E_WARNING (integer)	Runtime warning (non-fatal error). Only a prompt message is given, but the script does not terminate.
4	E_PARSE (integer)	Compile time syntax parsing error. Parsing errors are generated only by the parser.
8	E_NOTICE (integer)	Runtime notification. Indicates that the script encounters a situation that may appear as an error, but there may also be similar notifications in scripts that can run normally.
16	E_CORE_ERROR (integer)	A fatal error that occurred during PHP initialization startup. This error is similar to E_ERROR, but is generated by the PHP engine core.	since PHP 4
32	E_CORE_WARNING (integer)	Warning (non-fatal error) occurred during PHP initialization startup. Similar to E_WARNING, but generated by the PHP engine core.	since PHP 4
64	E_COMPILE_ERROR (integer)	Fatal compile time error. Similar to E_ERROR, but generated by the Zend script engine.	since PHP 4
128	E_COMPILE_WARNING (integer)	Compile time warning (non-fatal error). Similar to E_WARNING, but generated by the Zend scripting engine.	since PHP 4
256	E_USER_ERROR (integer)	User-generated error message. Similar to E_ERROR, but is generated by the user using the PHP function trigger_error() in the code.	since PHP 4
512	E_USER_WARNING (integer)	User-generated warning message. Similar to E_WARNING, but is generated by the user using the PHP function trigger_error() in the code.	since PHP 4
1024	E_USER_NOTICE (integer)	Notification information generated by the user. Similar to E_NOTICE, but is generated by the user using the PHP function trigger_error() in the code.	since PHP 4
2048	E_STRICT (integer)	Enable PHP's suggestions for code modifications to ensure the best interoperability and forward compatibility of the code.	since PHP 5
4096	E_RECOVERABLE_ERROR (integer)	A fatal error that can be caught. It indicates that a potentially dangerous error has occurred, but has not caused the PHP engine to become unstable. If the error is not caught by a user-defined handler (see set_error_handler()), it will become an E_ERROR and the script will terminate.	since PHP 5.2.0
8192	E_DEPRECATED (integer)	Runtime notification. When enabled, a warning will be given about code that may not work properly in future versions.	since PHP 5.3.0
16384	E_USER_DEPRECATED (integer)	User generated warning message. Similar to E_DEPRECATED, but is generated by the user using the PHP function trigger_error() in the code.	since PHP 5.3.0
30719	E_ALL (integer)	E_STRICT all error and warning messages.	30719 in PHP 5.3.x, 6143 in PHP 5.2.x, 2047 previously

Error level

(1) Deprecated

Output

<code>if (ereg('/llo/', 'hello world')) {
    echo 'yes2';
} else {
    echo 'no2';
}
</code>

(3) Warning warning level

<code>Deprecated: Function ereg() is deprecated in /Users/weiheli/www/php/003.php on line 3
no
</code>

output

<code>$arr = ['a'=>'aaa', 'b'=>'bbb'];
echo $arr[a];
</code>

(4) Fatal error fatal level

<code>Notice: Use of undefined constant a - assumed 'a' in /Users/weiheli/www/php/003.php on line 4
aaa
</code>

output

<code>settype($var, 'abc');
echo $var;
</code>

(5) Parse error parsing error

<code>Warning: settype(): Invalid type in /Users/weiheli/www/php/003.php on line 3
</code>

output

<code>// 调用未定义的函数
fn(12);
</code>

(6) E_USER_ user Level errors

configuration errors

<code>Fatal error: Call to undefined function fn() in /Users/weiheli/www/php/003.php on line 3
</code>

can be set at runtime with the error_reporting directive

<code>echo 'hello world'
</code>

or can be set using the

ini_set

function

user-thrown errors

<code>Parse error: parse error, expecting `','' or `';'' in /Users/weiheli/www/php/003.php on line 3
</code>

loggingconfiguration in php.ini

<code>; 是否显示错误。解析错误始终都会显示
display_errors = On

; 显示哪些错误
;error_reporting = E_ALL & ~E_DEPRECATED & ~E_STRICT
error_reporting = E_ALL
</code>

Logging function

<code>error_reporting()
</code>

Customized error handling

<code>trigger_error(string $error_msg [, int $error_type = E_USER_NOTICE ])
</code>

Exception

<code>是否记录错误日志
log_errors = On

错误日志最大字节数
log_errors_max_len = 1024

是否忽略重复错误
ignore_repeated_errors

是否忽略重复信息来源
ignore_repeated_source

保存到系统日志中
error_log = syslog
</code>

As you can see from the above code, exceptions will not be automatically thrown in PHP. You must use

throw

---

, which is different from Java

<code>error_log()

openlog() 
syslog()
closelog() 
</code>

Built-in exception classes such as PDO are not used

throw

throwThe statements after will not be executed

try cannot be used independently

<code>set_error_handler — 设置一个用户定义的错误处理函数
</code>

Customized exception handling

<code>try {
    $num = 1 / 0;
} catch (Exception $e) {
    echo $e->getMessage();
}

Warning: Division by zero in /Users/weiheli/www/php/003.php on line 4
</code>

Copyright statement: This article is an original article by the blogger, No reproduction is allowed without the permission of the blogger.

---

The above has introduced the errors and exceptions in PHP, including related content. I hope it will be helpful to friends who are interested in PHP tutorials.