Upload File using ist and use that into PHP method

gistfile1.txt

//js code
    $('.file-field:file').on('change', function() {
        var file_data = this.files[0];   
        var form_data = new FormData();                  
        form_data.append('file', file_data);
        var formUrl = 'upload.php';
        $.ajax({
            url: formUrl,
            dataType: 'text',
            cache: false,
            contentType: false,
            processData: false,
            data: form_data,                         
            type: 'post',
            success: function(response){
                console.log(response);
            }
         });
    });
    
//php code
public function save_file_data()
{
  // logic over here
}