为什么php文件编码影响响应数据编码？

Question

I make simple web server responsing JSON string with PHP.

It had worked well until I changed some php files with Notepad++.

From the moment I changed some php files with Notepad++, my mobile client have made the error

CompanyName.ProjectName.V1.Client.ApiException: Unexpected character encountered while parsing value: . Path ", line 0, position 0.`.

I solved this problem, deleting 'UTF-8 BOM(Binary Order Mask)' at first of php files.

But, as far as I know PHP is script language. Why PHP file encoding influence response data encoding? In Python, same script language like PHP, there is no problem with file encoding.

Because I don't know much about PHP, I wonder why that happened.

Answer 1

PHP expects scripts to conform to the Unicode standard. According to the Unicode standard, the BOM for UTF-8 files is not recommended:

2.6 Encoding Schemes

Use of a BOM is neither required nor recommended for UTF-8, but may be encountered in contexts where UTF-8 data is converted from other encoding forms that use a BOM or where the BOM is used as a UTF-8 signature. See the “Byte Order Mark” subsection in Section 16.8, Specials, for more information.

Hat tip: What's different between UTF-8 and UTF-8 without BOM?

You may want to consider using editing software that correctly deals with PHP. I like Atom (https://atom.io/), a free, open source software that supports PHP and many other languages.