php - PHP Division by Zero

Question

I have the following PHP code to display my tag cloud. It seems if I don't have at least two tags that are the same, I get a warning message saying Warnng: Division by zero (shown below).

Could some one please help me fix this code? Thank you!

<?php
// define variables
$fontSizeUnit = "px";
$maxFontSize = 40;
$minFontSize = 10;
$tagsToDisplay = 100;
$tagDivider = " ";

// font size range
$fontSizeSpread = $maxFontSize - $minFontSize;

// create blank arrays
$tagArray = array();
$tempTagArray = array();

// DB: get all public tags
$result = mysqli_query($conn, "SELECT Tags FROM blog WHERE Tags != '' AND IsPublic = 1 ORDER BY RAND()")
or die($dataaccess_error);

if(mysqli_num_rows($result) > 0 )
{
    // loop through results
    while($row = mysqli_fetch_array($result))
    {
        // split the results
        $tempStringArray = preg_split("/,/", $row['Tags']);

        // loop through all items of this string array
        for ($a = 0; $a < count($tempStringArray); $a++) 
        {
            // convert to lowercase
            $tempStringArray[$a] = strtolower($tempStringArray[$a]);

            // check if it exists in tag array
            if (empty($tagArray[$tempStringArray[$a]])) 
            {
                // if it doesn't exist, create it with value 1
                $tagArray[$tempStringArray[$a]] = 1;
            } 
            else 
            {
                // if it does exist, increase the value by 1
                $tagArray[$tempStringArray[$a]] += 1;
            }
        }
    }

    // store to temporary array and sort descending
    arsort($tagArray);
    $numberOfTags = 0;

    foreach ($tagArray as $key => $val) 
    {
        $numberOfTags++;

        if ($numberOfTags > $tagsToDisplay) 
        {
            break;
        }

        $finalTagArray[$key] = $val;
    }

    ksort($finalTagArray);

    $maxTagCount = max($finalTagArray);
    $minTagCount = min($finalTagArray);

    $tagCountSpread = $maxTagCount - $minTagCount; // <<== Problem here...

    $unitsPerCount = $fontSizeSpread/$tagCountSpread;

    // function to calculate the font size
    function calcSize($thisTagCount) {

        // import necessary global variables
        global $minTagCount, $minFontSize, $fontSizeUnit, $unitsPerCount;

        // calculate font size
        $thisFontSize = $minFontSize+($unitsPerCount*($thisTagCount-$minTagCount));

        // round font size and add units
        $thisFontSize = round($thisFontSize) . $fontSizeUnit;

        // return font size
        return $thisFontSize;

    }

    // echo out the resulting tags
    $b = 1;
    foreach ($finalTagArray as $key => $val) 
    {
        echo "<a href='snippets-by-tags.php?tag=".urlencode($key)."' style='font-size: ";
        echo calcSize($val);
        echo "'>" . htmlentities($key) . "</a>";

        if($b != count($finalTagArray)) 
        {
            echo " " . $tagDivider . " ";
        }
        $b++;
    }
}
else
{
    echo '<a href="#">none found ...</a>';
}
?>

score 4 · Accepted Answer

あなたの問題は実際にはこの行にあります：

$unitsPerCount = $fontSizeSpread/$tagCountSpread;

$tagCountSpread がゼロの場合、これはゼロによる除算です。それは、$maxTagCountと$minTagCountが同じ場合に発生します。

これを防ぐ必要があります：

if ($tagCountSpread != 0)
{
  $unitsPerCount = $fontSizeSpread / $tagCountSpread;
}
else
{
  // sensible recovery code
}

score 4 · Accepted Answer

が 0かどうかを確認する必要$tagCountSpreadがあります。明らかに 0 = 無限で除算します。(したがって、エラーが発生します)。これは手っ取り早い解決策かもしれませんが、アプリケーションに適した解決策を真剣に考える必要があります。

 if ($tagCountSpread <= 0) $tagCountSpread = 1;
 $unitsPerCount = $fontSizeSpread/$tagCountSpread;

score 1 · Accepted Answer

// ...

$minTagCount = min($finalTagArray);

if(($tagCountSpread = $maxTagCount - $minTagCount) === 0){

    // do something else when its zero; throw an exception, throw a party... whatever

}

// otherwise continue

$unitsPerCount = $fontSizeSpread/$tagCountSpread;

// ...

score 1 · Accepted Answer

PHP は、それがどの行で発生したかを表示し、なぜそれがゼロで除算されているのかを突き止め、それを修正します (おそらくいくつかの条件を使用します)。

score 0 · Accepted Answer

おそらくあなたの問題は次の行です：

$unitsPerCount = $fontSizeSpread/$tagCountSpread;

そして前のものではありません。NULL (0)かどうかを確認$tagCountSpreadし、そうでない場合は除算を行う必要があります。

if($tagCountSpread != 0)
{
     $unitsPerCount = $fontSizeSpread/$tagCountSpread;
}else{
     ///something
}

php - PHP Division by Zero

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