$ope = "<6";
        $num = 4;
        $opt ='$result=' . $num . $ope . ';';
        eval($opt);
        var_dump($result);

正则 /^(.+?)(d+)$/

如果你的$ope和$num严格按照题目的格式来的话，感觉可以构造成表达式用eval函数来执行

$ope = ">6";
$num = 4;
$expression = "echo ".$num.$ope.";";
$result = eval($expression);
echo $result;