How to solve the problem of PHP+trim garbled characters

PHP trim garbled characters are because string functions in PHP are not multibyte-safe by default. The solution is to encapsulate an mb_trim function to solve the garbled characters.

#The operating environment of this article: Windows 7 system, PHP version 7.4, Dell G3 computer.

How to solve the problem of PHP trim garbled characters?

PHP's Trim intercepts garbled characters

Always use Trim to filter strings at both ends. The official description of Trim:

trim — Remove blank characters (or other characters) at the beginning and end of the string

I found a very strange problem today, the code is as follows:

<?php
$str = &#39;研发、产品、&#39;;
echo trim($str, &#39;、&#39;);

Guess what this will return? "Devolop product"? NO, this one strangely returned to "R&D and production".

Could it be that my opening method is wrong? How come garbled characters are returned?

After some testing, I found a very interesting problem.

<?php
echo trim(&#39;abacabb&#39;, &#39;ab&#39;);   //print &#39;c&#39;

I originally thought this would return acabb, but it only returned c. This is a misunderstanding of the trim function.

Actually, this example is available in the official documentation, but I didn’t pay attention to it.

trim will loop through the first characters of the string. As in the above example, the execution process is as follows:

The string abacabb will start looping from subscript 0. If the characters in ab exist, they will be removed. The loop will stop when there are no characters in ab.

So the execution is:

• Loop a exists in the string ab, remove it, leaving bacabb

• Loop b exists In the string ab, remove it, leaving acabb

• loop a exists in the string ab, remove it, leaving cabb

• loop c does not It exists in the string ab and stops the loop, so after removing the first character, what remains: cabb.

But trim filters the first and last characters, so it will also be removed from the end in a loop.

• Loop b exists in the string ab, remove it, and the remaining cab is

• Loop b exists in the string ab, remove it, and the remainder ca,

• Loop a exists in string ab, remove it, leaving c,

• Loop c does not exist in string ab, stop loop, so removing the terminal character leaves: c.

So after the whole thing is over, abacabb is left with c. See here you have some understanding of the trim function.

Okay, let’s talk about the problem of garbled codes. Why are garbled codes returned?

This is because in PHP, string functions are not multibyte-safe by default. If you need multibyte-safe, you need to use the mb_ series of functions.

The hexadecimal code of "," is 0xe3 0x80 0x81. Functions that are not multibyte-safe will treat it as three characters.

The hexadecimal code of "品" is 0xe5 0x93 0x81. The last 0x81 here just matches and is filtered. This will lead to garbled characters.

ok, the problem is found, trim does not have the mb function, but we can encapsulate one ourselves. Function mb_trim.

PS: I have been using trim for a long time, but I have never really understood it. It is still important to read the official documentation.

Recommended learning: "PHP Video Tutorial"

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