Adding BOM to CSV file using fputcsv

Question

I have a simple CSV file being generated that includes foreign characters. I've noted that if I don't include a Byte Order Mark that the foreign characters aren't appearing properly in Excel (but they appear fine when a BOM is present).

How can I add a BOM to the beginning of the file when it's first created? I've tried the following and it's not working :-/

function processForm($competition, $competitionEntry) {
    $BOM = "\xEF\xBB\xBF"; // UTF-8 BOM

    $filename = $competition->ID.".csv";
    $file = "entries/".$filename;     

    $fields = array_keys($competitionEntry);
    $submittedForm = $competitionEntry;

    if(file_exists($file)) {
        $fp = fopen($file, 'a');
        if($fp && 
            fputcsv($fp, $submittedForm) && 
            fclose($fp)) {
            return true;
        } 
    } else { // CREATE NEW FILE
        $fp = fopen($file, 'w');
        if($fp && 
            fputcsv($fp, $BOM) && // WRITE BOM TO FILE   
            fputcsv($fp, $fields) &&
            fputcsv($fp, $submittedForm) &&
            fclose($fp)) {     
            return true;
        } 
    }
    return false;
}

Solution

Thanks to Mark Baker for this answer:

I needed to use fwrite() to add the BOM, not fputcsv().

The working version looks like this:

if(file_exists($file)) {
    $fp = fopen($file, 'a');
    if($fp && 
        fputcsv($fp, $submittedForm) && 
        fclose($fp)) {
        return true;
    } 
} else {
    $fp = fopen($file, 'w');
    fwrite($fp, $BOM); // NEW LINE
    if($fp &&    
        fputcsv($fp, $fields) &&
        fputcsv($fp, $submittedForm) &&
        fclose($fp)) {     
        return true;
    } 
}

Thanks, Mark!