Search a Earth back-side by lat-lon point

backside.php

<?php

function backSide($lat, $lon) {

	$lat *= -1;
	$lon = $lon < 0 ? $lon + 180 : $lon - 180;
	return [$lat, $lon];

}

// Usage:
print_r(
	baskSide(-58.603671, -130.343008)
);