Obviously $data is the string and we are removing the characters that satisfy the reg expression, but what characters are being specified by /[\xF0-\xF7].../ ?

 preg_replace('/[\xF0-\xF7].../', '', $data)

Also what what is the significance of these characters being replaced?

Edit for bounty: specifically, what exploit is this trying to prevent from occurring? The data is later used in mysql queries (non-pdo), so I presume some kind of injection attack is involved with these characters perhaps? Or not? I am trying to understand the logic behind this line of code in a script I am reading.

php mysql regex utf-8 sql-injection
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