Problems with Chinese character substitution and pattern matching in php! ! Please read it! _PHP Tutorial

Author: bluedoor
Original post address: http://www.anbbs.com/anbbs/index.php?f_id=3&page=1
I have been working on a keyword highlighting program for the past two days. I have written it. The program ran fine when tested locally, but as soon as I went up to the page, piles of garbled characters appeared. Let alone highlighting them, it was impossible to read them!
I looked for errors and searched again and again. I found that there was no problem with English, but it was easy to have problems when encountering Chinese characters. Sometimes there would be problems when encountering Chinese characters.
To summarize:
When using pattern matching, such as: preg_match_all($pat,...) and preg_replace($pat,...)...
The situations that are prone to problems are as follows:
preg_match_all("/(Chinese character)+/ism","I am a Chinese character, let's see what you do to me!",$m_a);
This pattern is very simple, it just matches "Chinese characters". In this case, the pattern containing Chinese characters can be successfully matched, but don't be too happy too early. The result is uncertain. Why are you not sure? Read on.
The problems that will occur are as follows:
preg_match_all("/[Chinese characters]+/ism","I am a Chinese character, let’s see what you do to me!",$m_a);
I want to match "Chinese characters" ", "zi" or "kanji". This is bound to cause problems. The matching results will be a bunch of garbled characters, and there may be an infinite loop. Why does this happen? This is because PHP does not use UNICODE internally and does not support multi-byte text, so a "Chinese character" is treated as a 4-byte ASCII for pattern matching. It would be strange if there is no error!
Later, I tried to rewrite the pattern matching, and found a seemingly (why do I say seemingly? Look later) method to solve the problem:
preg_match_all("/(汉|字)+/ism","我It’s a Chinese character, let’s see what you do to me! ",$m_a);
Writing like this can match "汉", "字" or "汉字", the result in $m_a
Array
(
[0] => Array
(
[0] => Chinese characters
)
[1] => Array
(
[0] => Chinese characters
)
)
How about a fully matched string appears! But it’s too early to be happy, and problems will often occur when using it in practice! I looked for the problem again and finally found the root of the problem! PHP does not support multi-byte text, so pattern matching and character operations are performed after internal code conversion (I don’t know if this is correct). Let’s give an example:
eregi_replace("性", "No", "Responsible"); This operation is to replace the word "gender" in the string "Responsible" with "No". What is the final result? Because there is no "sex" in "sense of responsibility", the result should be that "sense of responsibility" was returned without executing the replacement operation, but the result turned out to be "sense of responsibility"!