For loop with a condition

PHP
#1

O’, trying to create this SVG with PHP

image
image1920×1080 149 KB

Heres how I display the numbers (1-20)

<text text-anchor="middle" x="35" y="120">1</text>
<text text-anchor="middle" x="35" y="185">3</text>
<text text-anchor="middle" x="35" y="250">5</text>
<text text-anchor="middle" x="35" y="315">7</text>
<text text-anchor="middle" x="35" y="380">9</text>
<text text-anchor="middle" x="35" y="445">11</text>
<text text-anchor="middle" x="35" y="510">13</text>
<text text-anchor="middle" x="35" y="575">15</text>
<text text-anchor="middle" x="35" y="640">17</text>
<text text-anchor="middle" x="35" y="705">19</text>
....
..;. 
<text text-anchor="middle" x="487" y="120">2</text>
<text text-anchor="middle" x="487" y="185">4</text>
<text text-anchor="middle" x="487" y="250">6</text>
<text text-anchor="middle" x="487" y="315">8</text>
<text text-anchor="middle" x="487" y="380">10</text>
<text text-anchor="middle" x="487" y="445">12</text>
<text text-anchor="middle" x="487" y="510">14</text>
<text text-anchor="middle" x="487" y="575">16</text>
<text text-anchor="middle" x="487" y="640">18</text>
<text text-anchor="middle" x="487" y="705">20</text>

In order to do this with PHP, is this right?

for ($x = 1; $x < 20; $x++) {
   if($x % 2 == 1) {
  echo '<text text-anchor="middle" x="35" y="'.(120 + (($x - 1 ) * 32.5)).'">'.$x.'</text>';
	}  else {
	  echo '<text text-anchor="middle" x="487" y="'.(120 + (($x - 2 ) * 32.5)).'">'.$x.'</text>';
	}
echo "\r\n";
}
#2

Does it work? Yes.

Could it be simplified? Yes.

Do you care?

#3

Aside from not actually going to 20, does it produce the result you want?

If you apply Don’t Repeat Yourself (DRY) coding, and only write logic for things that change - you have a starting x and y value, that you are adding/resetting offsets to, to arrive at the coordinates. You can do it this way -

$x0 = 35; // start
$x1 = 452; // offset

$y0 = 120; // start
$y1 = 65; // offset

// initial values
$x = $x0;
$y = $y0;
foreach(range(1,20) as $n)
{
	echo "<text text-anchor='middle' x='$x' y='$y'>$n</text>\r\n";
	
	// next column
	$x += $x1;
	// end of row
	if($n % 2 == 0)
	{
		$x = $x0; // reset column
		$y += $y1; // next row
	}
}
#4

For any given index $n;
$x = 35+(($n-1) % 2 * 452);
$y = 120+floor(($n-1) / 2)*65;

(This is also a good example of why 0-indexing is helpful for maths sometimes/often.)

1 Like
#5

thanks, thats such a better way to think about it.