PHP生成的png背景问题

我的php知识非常有限。。。因此，我搜索、找到并编辑了一个脚本，在png上编写文本，但透明度不存在：

<?php
$string = "username";
$string2 = "example.com";
$image = imageCreateFromPng("http://i.imgur.com/Y6hWkkW.png");
$cor = imagecolorallocate($image, 0, 0, 0);
imagestring($image,5,126,22,urldecode($string),$cor);
header('Content-type: image/png');
imagepng($image,NULL);

$stype = "png";

if ($stype = "png")
{
    // integer representation of the color black (rgb: 0,0,0)
    $background = imagecolorallocate($image, 0, 0, 0);
    // removing the black from the placeholder
    imagecolortransparent($image, $background);

    // turning off alpha blending (to ensure alpha channel information 
    // is preserved, rather than removed (blending with the rest of the 
    // image in the form of black))
    imagealphablending($image, false);

    // turning on alpha channel information saving (to ensure the full range 
    // of transparency is preserved)
    imagesavealpha($image, true);
}
?>

理想形象

我一直在网上搜索，但找不到解决方法 如果可以的话，请花点时间帮我

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非常感谢

您需要“启用”透明度

$string = "username";
$string2 = "example.com";
$image = imageCreateFromPng("http://i.imgur.com/Y6hWkkW.png");
$cor = imagecolorallocate($image, 0, 0, 0);
$background = imagecolorallocate($image, 0, 0, 0);
imagecolortransparent($image, $background);
imagealphablending($image, false);
imagesavealpha($image, true);
imagestring($image,5,126,22,urldecode($string),$cor);
header('Content-type: image/png');
imagepng($image,NULL);

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请尝试以下内容：@newboyhun尝试并更新了代码，虽然没有成功，但感谢您解决了输入透明度问题，非常感谢！你能帮我提示一下吗？