Php 如何重新调整图像的大小以保持高宽比并将其上载

我有一个按钮，可以将背景图像上传到文件夹中，并将文件名保存到数据库中，但我不知道在上传之前如何重新调整图像的大小。实际上我面临两个问题。 1-如何调整图像大小并上载。 2-如何将图像显示为具有不同维度的div的背景图像

我到目前为止所做的：

Html

<div class="image_load_div">
 <form id="imageform" enctype="multipart/form-data" method="post" action="upload.php">
   <input name="photoimg" id="photoimg" type="file"/>
 </form>
</div>

php-上传文件

$valid_formats = array("jpg", "png", "gif", "bmp");
if(isset($_POST) and $_SERVER['REQUEST_METHOD'] == "POST") {
   name = $_FILES['photoimg']['name'];
   $size = $_FILES['photoimg']['size'];
   if(strlen($name)) {
 list($txt, $ext) = explode(".", $name);
 if(in_array($ext,$valid_formats)) {
   if($size<(1024*1024)) {
          session_start();
      $id = $_SESSION['QuestionId'];
      $path = "/images/Img/".$id."_bg.".$ext;

          if( move_uploaded_file($_FILES["photoimg"]["tmp_name"],$path) ) {
             // Save the file name into database
          }
        else { echo "<script>alert('Upload failed');</script>"; }
   else { echo "<script>alert('Image file size max 1 MB');</script>"; }                 
    else {  echo "<script>alert('Invalid file format..');</script>"; }  
 else { echo "<script>alert('Please select image..!');</script>";   exit; }

$valid_formats=数组（“jpg”、“png”、“gif”、“bmp”）；
如果（isset（$\u POST）和$\u服务器['REQUEST\u METHOD']=“POST”）{
name=$\u文件['photoimg']['name']；
$size=$\u文件['photoimg']['size']；
if（strlen（$name））{
列表（$txt，$ext）=分解（“.”，$name）；
if（在数组中（$ext，$valid_格式））{
如果（$size，您可以使用CSS进行此操作，并且仍然保持比例

<img src="image.png" style="max-width: 400px;">



然后，您可以使用php将图像的大小缩小为最大尺寸，然后使用CSS对其大小进行微调，这是一个有效且经过良好测试的代码。希望它能为您提供帮助

调用方法E：

$newname="xyz";
$filename=$_FILES['featured-img']['name'];
$extension=strtolower(substr(strrchr($filename, '.'), 1)); //Get extension
$extension=trim($extension);
$newfilename=$newname.$extension;
$newfilename=preg_replace('/\s+/', '_',$newfilename);

$target1 = "directory_path".$newfilename;
if(move_uploaded_file($_FILES['featured-img']['tmp_name'],$target1));   
scaleImage($target1,500, 350, $target1);

方法定义：

function scaleImage($source_image_path, $maxWidth, $maxHeight, $thumbnail_image_path){


          list($source_image_width, $source_image_height, $source_image_type) = getimagesize($source_image_path);
    switch ($source_image_type) {
        case IMAGETYPE_GIF:
            $source_gd_image = imagecreatefromgif($source_image_path);
            break;
        case IMAGETYPE_JPEG:
            $source_gd_image = imagecreatefromjpeg($source_image_path);
            break;
        case IMAGETYPE_PNG:
            $source_gd_image = imagecreatefrompng($source_image_path);
            break;
    }
    if ($source_gd_image === false) {
        return false;
    }
    $thumbnail_image_width=$maxWidth;
    $thumbnail_image_height=$maxHeight;


    $thumbnail_gd_image = imagecreatetruecolor($thumbnail_image_width, $thumbnail_image_height);
    imagecopyresampled($thumbnail_gd_image, $source_gd_image, 0, 0, 0, 0, $thumbnail_image_width, $thumbnail_image_height, $source_image_width, $source_image_height);
    imagejpeg($thumbnail_gd_image, $thumbnail_image_path, 90);
    imagedestroy($source_gd_image);
    imagedestroy($thumbnail_gd_image);
    return true;


}

function scaleImage($source_image_path, $maxWidth, $maxHeight, $thumbnail_image_path){


          list($source_image_width, $source_image_height, $source_image_type) = getimagesize($source_image_path);
    switch ($source_image_type) {
        case IMAGETYPE_GIF:
            $source_gd_image = imagecreatefromgif($source_image_path);
            break;
        case IMAGETYPE_JPEG:
            $source_gd_image = imagecreatefromjpeg($source_image_path);
            break;
        case IMAGETYPE_PNG:
            $source_gd_image = imagecreatefrompng($source_image_path);
            break;
    }
    if ($source_gd_image === false) {
        return false;
    }
    $thumbnail_image_width=$maxWidth;
    $thumbnail_image_height=$maxHeight;


    $thumbnail_gd_image = imagecreatetruecolor($thumbnail_image_width, $thumbnail_image_height);
    imagecopyresampled($thumbnail_gd_image, $source_gd_image, 0, 0, 0, 0, $thumbnail_image_width, $thumbnail_image_height, $source_image_width, $source_image_height);
    imagejpeg($thumbnail_gd_image, $thumbnail_image_path, 90);
    imagedestroy($source_gd_image);
    imagedestroy($thumbnail_gd_image);
    return true;


}