lib/PHPExif/Exif.php
public function getFocalLength()
    {
        if (!isset($this->data[self::FOCAL_LENGTH])) {
            return false;
        }

        return $this->data[self::FOCAL_LENGTH];
    }
public function getFocalLength()
    {
        if (!isset($this->data[self::FOCAL_LENGTH])) {
            return false;
        }

        return $this->data[self::FOCAL_LENGTH];
    }
Returns the focal length in mm, if it exists

@return float|boolean