strrchr(): Non-string needles will be interpreted as strings in the future. Use an explicit chr() call to preserve the current behavior – PHP Versions

am using PHP 7.3 and Am getting this error below

 data: {
           newItem: {st: '', nd: '', rd: '', th: ''},
           lot: "<?php echo e(substr('000' . $lot->id, strrchr('000' . $lot->id, 20), 4)); ?>",
           Tickets: [],
           cart: [],
           sel: ''
       },

I have not tried anything yet apart from changing to different php versions