html

<form action="admin/create_book.php" enctype="multipart/form-data">
<input type="file" name="file_img" accept="image/*">
</form>

js

$(document).ready(function(){
    $.ajax({
    url: "xxx.php",
    type: "POST",
    data: new FormData(this),
    contentType: false,
    cache: false,
    processData:false,
    })
    .done(function(data, textStatus, jqXHR) {//新增商品回傳到HTML成功的訊息
        console.log(data.name);
    });
});

PHP

$sourcePath = $FILES['fileimg']['tmpname'];
$targetPath1 = "../createimg/".$FILES['fileimg']['name'];//要上傳的路徑
if(moveuploadedfile($sourcePath,$targetPath1)){//照片上傳成功的時候
    echo jsonencode(['上傳成功'。]);
}else{
    echo jsonencode(['上傳失敗'。]); 
}