preg_last_error()

(PHP 5 >= 5.2.0, PHP 7)

返回最后一个PCRE正则执行产生的错误代码

说明

返回最后一次PCRE正则执行的错误代码。

preg_last_error()示例

以上例程会输出：

Backtrack limit was exhausted!

返回值

返回下面常量中的一个(查看它们自身的解释):

• PREG_NO_ERROR
• PREG_INTERNAL_ERROR
• PREG_BACKTRACK_LIMIT_ERROR（参见pcre.backtrack_limit）
• PREG_RECURSION_LIMIT_ERROR（参见pcre.recursion_limit）
• PREG_BAD_UTF8_ERROR
• PREG_BAD_UTF8_OFFSET_ERROR（自 PHP 5.3.0 起）
• PREG_JIT_STACKLIMIT_ERROR(自 PHP 7.0.0 起)

In PHP 5.5 and above, getting the error message is as simple as: 

Take it into account before use this function.
My php --version
PHP 5.6.29 (cli) (built: Dec 8 2016 09:19:46) 
Copyright (c) 1997-2016 The PHP Group
Zend Engine v2.6.0, Copyright (c) 1998-2016 Zend Technologies
On Linux Fedora 23 4.8.13-100.fc23.x86_64 #1 SMP Fri Dec 9 14:51:40 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux 

The above function pcre_error_deocde [sic] is not correct - not all of the used constants are errors constants. For example, when the error is actually PREG_BAD_UTF8_ERROR, the function outputs the text for PREG_SPLIT_OFFSET_CAPTURE.

Just an addition to my previous note: In unicode mode (with "u" modifier), PREG_BAD_UTF8_ERROR only reflects errors in the subject string. If the pattern itself contains invalid characters, preg_match() (or preg_match_all()) returns false but preg_last_error() returns 0 indicating PREG_NO_ERROR. Instead, php issues a warning: "preg_match(): Compilation failed: invalid UTF-8 string at offset 0"

Here is a correction to one of the previous "get error message" snippets. It filters out the non-error codes which stops "Warning: array_flip(): Can only flip STRING and INTEGER values!" from being emitted due to ["PCRE_JIT_SUPPORT"]=>bool(true):

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