elseif, as its name suggests, is a combination
    of if and else.  Like
    else, it extends an if
    statement to execute a different statement in case the original
    if expression evaluates to
    FALSE.  However, unlike
    else, it will execute that alternative
    expression only if the elseif conditional
    expression evaluates to TRUE.  For example, the
    following code would display a is bigger than
    b, a equal to b
    or a is smaller than b:
    
   
    There may be several elseifs within the same
    if statement.  The first
    elseif expression (if any) that evaluates to
    TRUE would be executed.  In PHP, you can also
    write 'else if' (in two words) and the behavior would be identical
    to the one of 'elseif' (in a single word).  The syntactic meaning
    is slightly different (if you're familiar with C, this is the same
    behavior) but the bottom line is that both would result in exactly
    the same behavior.
   
    The elseif statement is only executed if the
    preceding if expression and any preceding
    elseif expressions evaluated to
    FALSE, and the current
    elseif expression evaluated to
    TRUE.