使用 HEAD 方法验证给定 URL 是否是有效的图像/大小

<?php
$img_url = "example.com/image.jpg";
$headers = get_headers($img_url, 1);
$width = $headers['Content-Length'];
$height = 0;
$type = $headers['Content-Type'];
if ($type == 'image/jpeg') {
    $img = imagecreatefromjpeg($img_url);
    $width = imagesx($img);
    $height = imagesy($img);
} elseif ($type == 'image/png') {
    $img = imagecreatefrompng($img_url);
    $width = imagesx($img);
    $height = imagesy($img);
} elseif ($type == 'image/gif') {
    $img = imagecreatefromgif($img_url);
    $width = imagesx($img);
    $height = imagesy($img);
}
echo "Width: " . $width . "<br>";
echo "Height: " . $height;
?>