Why my datatable column search not working?

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Javascript

PHP

MySQL

hi,i am using a server side datatable where i fetch data from my sqldaabase. but my column search is not working.

What I have tried:

<script>
    $(document).ready(function() {
        $('#order_data thead th').each(function() {
            var title = $(this).text();
            $(this).html(title + ' <input type="text" class="col-search-input" placeholder="Search ' + title + '" />');
        });

        var table = $('#order_data').DataTable({
            "processing" : true,
    "serverSide" : true,
    "order" : [],
    "ajax" : {
     url:"fetch.php",
     type:"POST"
    },
    drawCallback:function(settings)
    {
     $('#total_order').html(settings.json.total);

    },
        });

        table.columns().every(function() {
            var table = this;
            $('input', this.header()).on('keyup change', function() {
                if (table.search() !== this.value) {
                    table.search(this.value).draw();
                }
            });
        });
    });
</script>