Why Does My PHP AJAX Callback Have an Extra Character (65279) at the Beginning?

Echoing of Character 65279 in PHP: Causes and Remedies

When performing an AJAX callback and comparing the XMLHTTP request response to a string, developers may encounter a discrepancy due to the presence of an invisible character prepended to the response. This character, often identified as 65279 using charCodeAt(0), is known as a UTF-8 control character indicating the encoding type.

To determine the origin of this character, it's crucial to understand that Windows Notepad adds a BOM (Byte Order Mark) to UTF-8 encoded files, consisting of three bytes (EF BB BF). While PHP does not explicitly handle the BOM, problems arise when including one PHP file into another.

Solution:

There are multiple options to resolve the issue:

1. Edit the File with Notepad : Use a text editor like Notepad that allows you to "Encode in UTF-8 without BOM."
2. Save the PHP File in ANSI Encoding: Save the PHP file in notepad with ANSI encoding (only suitable if it contains no extended characters).
3. Use the ini_set() Function: Set the ini_set('default_charset', 'UTF-8') option to explicitly specify the character encoding, ensuring consistent handling.

These solutions effectively remove the BOM character from the included file, preventing the unexpected addition of character 65279.

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