Graphical Calculator

<?php
function collatz($originalNumber){ //the collatz conjecture function
  $number = $originalNumber;
  do{
  $i++;
      if(1&$number){
        $number = (3*$number)+1;
      }else{
        $number = $number/2;
      }
  }while($number != 1);
  return floor($i);
}

//Your function
function yourFunction($x){
  return floor(pow(2, $x)-512);
}

echo "Name of Your Function\n"; // :D

//Your parameters
$domain = 10; //between 0 and 'x', doesn't plot negative values of X yet. :\
$lineThickness = 2;
$accuracy = 0.01; //lower the number, higher the accuracy

//---Begin main program
for($n = 0; $n <= $domain/$accuracy; $n++){
  $i = yourFunction($n*$accuracy); //testing how many steps that it will take for the number $n to reach 1.
  if($i > $maxheight || $n == 0){ //if the result is larger than all the  rest, the new result will become the largest result.
    $maxheight = $i;
  }
  if($i < $minheight || $n == 0){
    $minheight = $i;
  }
  echo $n*$accuracy." = $i\n";
  $x[$n] = $i; //$n is the position along the x-axis, $i is the position along the y-axis.
}
//---begin writing file
unlink("image.ppm"); //file that we will be editing, we are are deleting the file so we have a clean file to work on
$fh = fopen("image.ppm", 'a+'); //creates the image file that we will be editting and opens the file for appending

$width = $n; //width of the image is the largest number that was tested
$height = abs($minheight - $maxheight)+1; //height is the largest amount of steps that it took to reach zero

$startWrite = "P3\n# image.ppm\n".$width." ".$height."\n255"; //fomatting the ppm file
fwrite($fh, $startWrite);

for($k = 0; $k < $width*$height; $k++){
  $CurPx = $k%$n; //basic modulus to decide when a new line must be made
  if($k%5 == 0){ //basic formatting decides when a new line must be placed
    $Nl = " \n";
  }else{
    $Nl = " ";
  }
  if($CurPx == 0){
    $CurPy++;
  }
  $dist = $x[$CurPx] - ($maxheight-$CurPy+1);
  if($dist > -$lineThickness && $dist < $lineThickness){ //basic algebra, fuck I hate zero being counted as an integer
    $red = "255"; //if the if statement above reflects the array which was made on line 23, the pixel will be white
    $green = "255";
    $blue = "255";
  }elseif($CurPy == $maxheight+1){
    $red = "000";
    $green = "255";
    $blue = "000";
  }elseif($CurPy < $maxheight+1){
    $clr = str_pad(floor(255*($CurPy/$maxheight)), 3, "0", STR_PAD_LEFT);
    $red = $clr;
    $green = "000";
    $blue = "000";
  }else{
    $clr = str_pad(255-floor(255*(($CurPy-$maxheight)/$maxheight)), 3, "0", STR_PAD_LEFT);
    $red = "000"; //else, it will be black
    $green = $clr;
    $blue = "000";

  }
  $write = $Nl."$red $green $blue"; //the line that is to be outputted
    fwrite($fh, $write); //write the pixel to the file.
}
fclose($fh); //close the file, done!
?>