Merging transparent images on PHP - php

Question

I'm trying to merge of this images:
https://imgur.com/aURQax9 -- Base
https://imgur.com/a/cpiSc -- Marking
the result should look like this:
https://imgur.com/a/ri3zw
I'm getting an image that is removing all of the black color, but I'm unsure how to do this.
$numberOfImages = 2;
$x = 600;
$y = 600;
$background = imagecreatetruecolor($x, $y);
$black = imagecolorallocate($background, 0, 0, 0);
imagecolortransparent($background, $black);
$firstUrl = 'Images/Horses/First horses/Red Breeds/Paint/Adult/Overo/1/BayOvero1AD.png';
$secondUrl = 'Images/Horses/First horses/Red Breeds/Paint/Markings/PaintBlazeAD.png';
$outputImage = $background;
$first = imagecreatefrompng($firstUrl);
$second = imagecreatefrompng($secondUrl);
imagecopymerge($outputImage,$first,0,0,0,0, $x, $y,100);
imagecopymerge($outputImage,$second,0,$y,0,0, $x, $y,100);
imagepng($outputImage, './Images/BayOvero1AD.PaintBlazeAD.png');
imagedestroy($outputImage);
How can I update this so that the color isn't removed and that it merges very similarly to the finished image above?

Answer 1

I have just wrote this for you. One of the images posted was a jpg not a PNG, however that could be to do with imgur, therefore I had to resize it and remove some of the white. Which is why my result didn't look quite right when testing. But it should be fine with your original files:
As you can see, it added the second image above the first, and kept it in the correct posistion.
The code I used for this was:
<?php
$x = 600;
$y = 600;
$firstUrl = 'Images/Horses/First horses/Red Breeds/Paint/Adult/Overo/1/BayOvero1AD.png';
$secondUrl = 'Images/Horses/First horses/Red Breeds/Paint/Markings/PaintBlazeAD.png';
$Image1 = imagecreatefrompng($firstUrl);
$Image2 = imagecreatefrompng($secondUrl);
imagealphablending($Image1, true);
imagesavealpha($Image1, true);
imagecopy($Image1, $Image2, 0, 0, 0, 0, $x, $y);
imagepng($Image1, './Images/BayOvero1AD.PaintBlazeAD.png');
?>