来自数据blob的文件扩展名

Question

I have javascript code that detects when an image is pasted into a contenteditable field:

document.onpaste = function(event){
    var items=(event.clipboardData || event.originalEvent.clipboardData || event.dataTransfer).items;
    for(i in items){
        var item=items[i];
        if(item.kind==='file' && ~item.type.indexOf("image")){ //is file and is image
            event.preventDefault();
            var blob=item.getAsFile();
            console.log(item, blob);
            var data=new FormData();
            data.append('fname','imageFromClipboard'); //extension for file name??
            data.append('newImage',blob);
            sendImage(data); //just a $.POST request
        }
    }
}

And PHP code that receives the POST request for the image:

$image = $_FILES['newImage'];
$imageFileType = pathinfo($image["name"],PATHINFO_EXTENSION); // obviously doesn't work
$imageId = new ImageId();
$imageName = $imageId.".".$imageFileType;
// [... some checks on the file ...]
$targetFile = "../../images/uploads/{$imageName}";
if($imageOK && move_uploaded_file($image["tmp_name"],$targetFile)){ 
//[ do stuff ]

How do I get the file extension reliably from the blob? Should I do it with JS or PHP? Is it fine for all possible image file types to just split the MIME type ("image/png" for instance) at the slash and just use that as an extension?

Answer 1

Splitting the mime type should be ok. Only problem mime_content_type function deprecated.

mime_content_type — Detect MIME Content-type for a file (deprecated)

You will have to use finfo_file instead.

$finfo = finfo_open(FILEINFO_MIME_TYPE);
$ftype = finfo_file($finfo, $image["tmp_name"])