Urlencoded %22 added to the string on PHP Ajax call - why does this happen?

Question

I'm making an Ajax call to PHP, trying to receive a simple string:

$.ajax({

  type: 'POST',
  url: $(this).attr('action'),
  data: { x: imgX, y: imgY, w: imgW, h: imgH, file: fileName },
  cache: false,
  success: function(data) {

    $('.photo-wrapper').html('<div class="inner"><img src=imgs"' + data + '" /></div>');
    console.log('Es crop!!');
  },
  error: function(data) {

    console.log('Es no crop :(');
  }
})

In PHP I got:

$digits = '00001';
echo 'img-' . $digits . '.jpg';

If I log or alert the received data in JavaScript, it shows properly. However, the img src url I try to form adds '%22' ot the both ends of string.

I know it's url encoded ", but the problem is that I can't figure out why it shows. Is this problem in the PHP end or is this a problem with my Ajax call?

I've also tried str.replace to it, without any effect. How can I get rid of those in JavaScript?