Remove duplicated lines

This function removes all duplicated lines of a text file. That's it.

/**
 * RemoveDuplicatedLines
 * This function removes all duplicated lines of the given text file.
 *
 * @param     string
 * @param     bool
 * @return    string
 */
function RemoveDuplicatedLines($Filepath, $IgnoreCase=false, $NewLine="\n"){

    if (!file_exists($Filepath)){
        $ErrorMsg  = 'RemoveDuplicatedLines error: ';
        $ErrorMsg .= 'The given file ' . $Filepath . ' does not exist!';
        die($ErrorMsg);
    }

    $Content = file_get_contents($Filepath);

    $Content = RemoveDuplicatedLinesByString($Content, $IgnoreCase, $NewLine);

    // Is the file writeable?
    if (!is_writeable($Filepath)){
        $ErrorMsg  = 'RemoveDuplicatedLines error: ';
        $ErrorMsg .= 'The given file ' . $Filepath . ' is not writeable!';   
        die($ErrorMsg);
    }

    // Write the new file
    $FileResource = fopen($Filepath, 'w+');     
    fwrite($FileResource, $Content);       
    fclose($FileResource); 
}


/**
 * RemoveDuplicatedLinesByString
 * This function removes all duplicated lines of the given string.
 *
 * @param     string
 * @param     bool
 * @return    string
 */
function RemoveDuplicatedLinesByString($Lines, $IgnoreCase=false, $NewLine="\n"){

    if (is_array($Lines))
        $Lines = implode($NewLine, $Lines);

    $Lines = explode($NewLine, $Lines);

    $LineArray = array();

    $Duplicates = 0;

    // Go trough all lines of the given file
    for ($Line=0; $Line < count($Lines); $Line++){

        // Trim whitespace for the current line
        $CurrentLine = trim($Lines[$Line]);

        // Skip empty lines
        if ($CurrentLine == '')
            continue;

        // Use the line contents as array key
        $LineKey = $CurrentLine;

        if ($IgnoreCase)
            $LineKey = strtolower($LineKey);

        // Check if the array key already exists,
        // if not add it otherwise increase the counter
        if (!isset($LineArray[$LineKey]))
            $LineArray[$LineKey] = $CurrentLine;       
        else               
            $Duplicates++;
    }

    // Sort the array
    asort($LineArray);

    // Return how many lines got removed
    return implode($NewLine, array_values($LineArray));   
}

// Example 1
// Removes all duplicated lines of the file definied in the first parameter.
$RemovedLinesCount = RemoveDuplicatedLines('test.txt');
print "Removed $RemovedLinesCount duplicate lines from the test.txt file.";

// Example 2 (Ignore case)
// Same as above, just ignores the line case.
RemoveDuplicatedLines('test.txt', true