PHP GD 上傳圖片等比例縮放並儲存

<?php
$tmp = $_FILES['uploadfile']['tmp_name'];
$src = imagecreatefromjpeg($tmp);
list($w,$h) = getimagesize($tmp);
$maxW = 600;
$newW = $maxW; $newH = ($h/$w)*$maxW;
$dst = imagecreatetruecolor($newW, $newH);
imagecopyresampled($dst, $src, 0,0,0,0, $newW,$newH, $w,$h);
$filename = "images/".$_FILES['uploadfile']['name'];
imagejpeg($dst, $filename, 100);
imagedestroy($src); imagedestroy($dst);
?>

關鍵點：imagecopyresampled 高品質重採樣、維持長寬比、輸出品質 100。實務上需加入檔案型別檢查、錯誤處理、唯一檔名生成。