This is a simple class for calculating a personal biorhythm values given the birth date and the date of a given day of life.
The (most common) theory of biorhythm states that our daily lives are significantly affected by simple rhythmic cycles. When we are born, three cycles begin from zero point and then oscillate between -100 and 100 till we die. The physical period is 23 days long, emotional 28, and intellectual has period of 33 days. Beware of days when any curve crosses zero especially if two or three do this simultaneously.
This class computes the data that defines the three sinusiodal curves (physical, emotional, and intellectual) in range from -100 to 100.
If the gd library extension is installed the class also provides means to build a simple yet neat diagram.