如何使用AJAX将所选文件传递给PHP文件？

I have 2 forms:

• Form A contains field name, age, address, email and a hidden text field for the names of images which are going to be uploaded in form B.

• Form B contain an input type File so users can browse and select their photos.

• I used Jquery to trigger an function upload those images after they are selected.

• I'm stuck at the step passing the selected images array to the PHP file that handles upload progress via AJAX.

• I searched but there were no samples for my problem. I appreicate any help.

  <form action="upload_img.php" name="form_B" method="POST" enctype="multipart/form-data">
       Select images: <input type="file" name="selected_imgs[]" id="selected_imgs" multiple>
  </form>
  
  <script type="text/javascript">
      $(function() {
          $("input:file").change(function (){
              ajax_upload();
          });
      });
  </script>
  

You can try below code

function uploadFile(){
var file = $('#filetoupload');
var valid_extensions = /(\.jpg|\.jpeg|\.gif|\.doc|\.xls|\.txt|\.rtf|\.pdf)$/i;
var isvalid = true;
//for every file...
var input = document.getElementById('filetoupload');
for (var x = 0; x < input.files.length; x++) {
    if(!valid_extensions.test(input.files[x].name)){
        isvalid = false;
    }
}

if(isvalid == true ){ 
    var formData = new FormData();
    for (var x = 0; x < input.files.length; x++) {
        formData.append("filetoupload[]",input.files[x]);
    }

    $.ajax({
        url: 'localhost/upload.php',  //server script to process data
        type: 'POST',
        data: formData,
        cache: false,
        contentType: false,
        processData: false,
        dataType: "json",
        success:function (data){
            alert("File Uploaded");
            // data.src return from your server
            // so you can display image in page using <img> tag
        },
        error:function (data){ 
            alert("Error!");
        }
    });
}else{                
    alert("File format not supported!");
    return false;
}
return true;
}