When mb_convert_encoding function UTF-8 is converted to gbk, the question mark is raised when the space is changed.

When the mb_convert_encoding function UTF-8 is converted to gbk, the question mark of space is changed. how can this problem be solved? The question mark is changed when spaces are changed to question marks and other Chinese characters are normal. when the mb_convert_encoding function UTF-8 is converted to gbk, the question mark is changed when spaces are changed.
How can this problem be solved? Only spaces are converted into question marks, and other Chinese characters can be shared:
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Check the source code and check that the Space is not normal (0x20), but 0xA0: No-Break Space (that is, nbsp)
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You can't blame others if you're wrong.
$ Str = str_replace ("0xC2 0xA0", '', $ str );
Should be
$ Str = str_replace ("\ xC2 \ xA0", '', $ str );