Tell the admissions panel a little bit about yourself. An SOP's primary objective is to provide a personal statement about you.
In your SOP for a PhD, try to address every justification for obtaining a PhD. Describe your motivations for pursuing this degree.
Describe or tell how your interest or passion in this particular field first came about in the introduction.
Mention your educational background in brief, beginning with your bachelor's degree.
Try to address any shortcomings you may have in your prior qualifications directly in your SOP if you have any.