The BLOB is the binary image. You can write that image to your filesystem once it's on your server. So if your image is in the variable $my_blob, you would do something like
file_put_contents('/path/to/new/file_name', $my_blob);
and there you go.
You might want to save the file to a tmp location first, then do some checks on it before you move it to a final location (with PHPs rename() function).
Btw: why not just save the BLOB to DB? That is a legitimate way of handling files these days, that's what the BLOB MySQL data type is for after all.
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