Question

I have a few points. I need to put those points on a circle and get their coordinates.

function positionX($numItems,$thisNum){ 
  $alpha = 360/$numItems; // angle between the elements
  $r = 1000; // radius
  $angle = $alpha * $thisNum; // angle for N element
  $x = $r * cos($angle); // X coordinates
  return $x;
}

function positionY($numItems,$thisNum){ 
  $alpha = 360/$numItems; // angle between the elements
  $r = 1000; // radius
  $angle = $alpha * $thisNum; // angle for N element
  $y = $r * sin($angle); // Y coordinates
  return $y;
}

But my code isn’t work.. These functions produce strange coordinates.

image example: http://cl.ly/image/453E2w1Y0w0d

UPD:

echo positionX(4,1)."<br>";
echo positionY(4,1)."<br><br>";

echo positionX(4,2)."<br>";
echo positionY(4,2)."<br><br>";

echo positionX(4,3)."<br>";
echo positionY(4,3)."<br><br>";

echo positionX(4,4)."<br>";
echo positionY(4,4)."<br><br>";

4 – All elements;
1,2,3,4 – Number of element.

These code gives me result:

-448.073616129
893.996663601

-598.460069058
0

984.381950633
-176.045946471

-283.691091487
958.915723414

On the circle it does not work.

Answer 1

The cos() and sin() functions expect the argument in radians, not in degrees.

Use the deg2rad() function to convert

EDIT

CODE:

function positionX($numItems,$thisNum){
  $alpha = 360/$numItems; // angle between the elements
  $r = 1000; // radius
  $angle = $alpha * $thisNum; // angle for N element
  $x = $r * cos(deg2rad($angle)); // X coordinates
  return $x;
}

function positionY($numItems,$thisNum){
  $alpha = 360/$numItems; // angle between the elements
  $r = 1000; // radius
  $angle = $alpha * $thisNum; // angle for N element
  $y = $r * sin(deg2rad($angle)); // Y coordinates
  return $y;
}

echo round(positionX(4,1))."<br>";
echo round(positionY(4,1))."<br><br>";

echo round(positionX(4,2))."<br>";
echo round(positionY(4,2))."<br><br>";

echo round(positionX(4,3))."<br>";
echo round(positionY(4,3))."<br><br>";

echo round(positionX(4,4))."<br>";
echo round(positionY(4,4))."<br><br>";

RESULTS:

0
1000

-1000
0

-0
-1000

1000
-0