fixed it up for you, had several syntax errors causing issues also using count() instead of num_row()
<?php
$columns = 2;
if(isset($_GET['member'])) {
$display = ceil(count($_GET['member']));
$rows = ($display / $columns);
while ($row = $display) {
$data[] = $row;
}
echo "<table border='1'>";
for($i = 0; $i < $rows; $i++) {
echo "<tr>";
for($j = 0; $j < $columns; $j++) {
if(isset($data[$i + ($j * $row)])) {
echo "<td>".$data[$i + ($j * $row)]."</td>";
$count = $count+1;
}
}
echo "</tr>";
}
}
?>