(PECL ps >= 1.1.0)
ps_arc — Draws an arc counterclockwise
$psdoc,$x,$y,$radius,$alpha,$beta
Draws a portion of a circle with at middle point at
(x, y). The arc starts at an
angle of alpha and ends at an angle of
beta. It is drawn counterclockwise (use
ps_arcn() to draw clockwise). The subpath added
to the current path starts on the arc at angle alpha
and ends on the arc at angle beta.
psdocResource identifier of the postscript file as returned by ps_new().
xThe x-coordinate of the circle's middle point.
yThe y-coordinate of the circle's middle point.
radiusThe radius of the circle
alphaThe start angle given in degrees.
betaThe end angle given in degrees.
成功时返回 true， 或者在失败时返回 false。