PHP：ImageCopy PNG问题

Question

I am trying to merge an image with transaprent edges into another image. Unfortunately, I have a grid that appears around this one. An idea ?

$source1 = imagecreatefrompng($name1);
imagealphablending($source1, false);
imagesavealpha($source1,true);

$source3= imagecreatefrompng($id.".final2.png");
imagealphablending($source3, false);
imagesavealpha($source3,true);

imagecopy($source1,$source3,250,250,0,0,500,500);

imagealphablending($source1, false);
imagesavealpha($source1, true);

imagepng($source1,$id.".finalz.png");

Best regards,

Concerned image here

P.S : After upload the color around the central image is gray but it is an image with a transparent grid outside the circle.