PHP + GD 2.3.3 vs PHP + GD bundles (2.1.0 compatible) gif transparency problem

pgp_gd_transparent_gif_and_png.php

<?php

// Create transparent gif in certain sizes and print out base64

$gd_version = gd_info()["GD Version"];
// check: bundled -> use a transparency, if not and 2.3.3 or higher, use alternate
$use_imagecolorallocatealpha = true;
if (strstr($gd_version, "bundled") !== false) {
	$use_imagecolorallocatealpha = false;
}

// demo sizes
$size_list = [
	[210, 296],
	[220, 340],
	[220, 440],
];
$type_gif = 'gif';
$type_png = 'png';

$save_file = $_GET['save_file'] ?? 0;
$g_width = $_GET['width'] ?? 0;
$g_height = $_GET['height'] ?? 0;
if (
	is_numeric($g_width) && $g_width > 0 && $g_width < 1000 &&
	is_numeric($g_height) && $g_height > 0 && $g_height < 1000
) {
	$size_list = [
		[$g_width, $g_height]
	];
} else {
	echo "Set Custom with _GET: width= and height=<br>";
}

foreach ($size_list as $size) {
	$width = $size[0];
	$height = $size[1];
	$im_gif = imagecreatetruecolor($width, $height);
	$im_png = imagecreatetruecolor($width, $height);
	// set always
	imagesavealpha($im_gif, true);
	imagealphablending($im_gif, true);
	imagesavealpha($im_png, true);
	imagealphablending($im_png, true);

	// if bundled, use "old style"
	if (!$use_imagecolorallocatealpha) {
		// does not work: GIF: 2.3.3, works for GIF on bundled
		$black_alpha_gif = imagecolorallocate($im_gif, 0, 0, 0);
		$transparent_w = imagecolortransparent($im_gif, $black_alpha_gif);
	} else {
		// does work: GIF: 2.3.3
		$black_alpha_gif = imagecolorallocatealpha($im_gif, 0, 0, 0, 127);
	}
	// gif fill
	imagefill($im_gif, 0, 0, $black_alpha_gif);
	// PNG, same for both is ok
	$black_alpha_png = imagecolorallocatealpha($im_png, 0, 0, 0, 127);
	imagefill($im_png, 0, 0, $black_alpha_png);

	ob_start();
	imagegif($im_gif);
	$image_data_gif = ob_get_contents();
	ob_end_clean();
	ob_start();
	imagepng($im_png);
	$image_data_png = ob_get_contents();
	ob_end_clean();

	// write
	if ($save_file) {
		imagegif($im_gif, 'images_output/' . $width . 'x' . $height . '.gif');
		imagepng($im_png, 'images_output/' . $width . 'x' . $height . '.png');
	}
	imagedestroy($im_gif);
	imagedestroy($im_png);
	// output
	echo "Width: <b>$width</b>, Height: <b>$height</b><br>";
	echo "<i>Base64 string GIF:</i><br>";
	echo '<div style="word-wrap: anywhere; font-family: monospace">';
	echo 'data:image/' . $type_gif . ';base64,' . base64_encode($image_data_gif);
	echo "</div>";
	echo "<i>Base64 string PNG:</i><br>";
	echo '<div style="word-wrap: anywhere; font-family: monospace">';
	echo 'data:image/' . $type_png . ';base64,' . base64_encode($image_data_png);
	echo "</div>";
	echo '<hr>';
}