NaN是php输出

我面临一个小问题，但不幸的是无法解决它

$rank = 13;  //Sometimes empty or Null
$hits = 3; //Sometimes empty or Null
$rating = $rank/$hits;
if(is_nan($rating)){
  $ratings = 0;
}
if(is_numeric($rating)  ){
  $ratings = number_format((float)$rating, 2, '.', ''); 
}else{
  $ratings = 0;  
}
$res['rating'] = $ratings; 

---

如果$rank或$hits为空，我将获得NaN作为输出。我做错了什么？

因为您必须检查$hits的数量，使其不被零除

<?php
$rank = 13;  //Sometimes empty or Null
$hits = 3; //Sometimes empty or Null

function isOkRankandHits($hank, $hits){
    if(isset($hank) && isset($hits)) //Check if hank or hits are not null
    return is_numeric($hits) && is_numeric($hank) && $hits > 0; //OK, you can make the division.
    //You don't specify if hank could have negative values
    return false;
}

$ratings = 0; //for security and maintenance, always work with a default value

if(isOkRankandHits($rank, $hits)){ // ratings will be numeric
$ratings = $rank / $hits;
$ratings = number_format((float)$ratings, 2, '.', ''); 
}

$res['rating'] = $ratings; 
?>

您不能通过检查异常“除零”来检查任何样本代码。我已经用$hank和$hits测试了数字、空值和字符串值。对我来说，这段代码正在运行。php不能被零除。你会有一个错误
<?php
$rank = NULL;  //Sometimes empty or Null
$hits = NULL; //Sometimes empty or Null
if(empty($rank))$rank =0;
if(empty($hits)){
  $ratings =0;
} else {
  $rating = $rank/$hits;
  $ratings = number_format((float)$rating, 2, '.', ''); 
}


echo $ratings; 
?>