Assist Please for meta data 'formula'

[*content:limit=`100`:notags*]

$sql = 'SELECT id,content FROM modx_site_content';
$result = mysql_query($sql);
while ($row = mysql_fetch_assoc($result)) {
    $desc = substr($row['content'], 0, 100);
    // further sanitize the string if necessary to strip tags etc.
    $query = "UPDATE modx_site_content SET description = $desc WHERE id = $row['id']";
    mysql_query($query);
}

<?php

/**
 * Fix HTML tags on the specified characters.
 * @param   string  $text   content
 * @return \tidy
 */
function properHTML($text) {
    if (!class_exists('tidy')) {
        return $text;
    }
    // Tidy
    $tidy = new tidy;

    /**
     * Change this
     * @link    http://tidy.sourceforge.net/docs/quickref.html
     */
    $tidyConfig = array();

    $tidy->parseString($text, $tidyConfig);
    $tidy->cleanRepair();

    if ($tidy->errorBuffer) {
        $errorBuffer = "There are some errors!\n";
        $errors = explode("\n", $tidy->errorBuffer);
        foreach ($errors as $error) {
            $errorBuffer .= $error . "\n";
        }
        echo $errorBuffer;
    }
    return $tidy;
}

///////////////// CHANGE THIS !!!!!!! ///////////////
$host = 'localhost';
$userhost = 'root';
$passhost = '123';

$mysql = mysqli_connect($host, $userhost, $passhost);
if (!$mysql) {
    die('<strong>Database connection error: </strong>' . mysqli_error());
}
///////////////// CHANGE THIS !!!!!!! ///////////////
$db = 'change_with_your_db_name';
$table = 'modx_site_content';

$select = mysqli_select_db($mysql, $db);
if (!$select) {
    die('<strong>Can not select database.</strong>');
}

$query = "SELECT id, description, content from " . $table;

$result = mysqli_query($mysql, $query);
if (!$result) {
    die('<strong>Query is failed.</strong>');
}

///////////////// CHANGE THIS !!!!!!! ///////////////
// Add more doc's IDs if you want to skip them
$ignoreIds = array(1);

while ($l = mysqli_fetch_assoc($result)) {
    if (empty($l['description']) &&
            !in_array($l['id'], $ignoreIds)
    ) {
        /**
         * substr: strip by characters
         */
        $description = substr($l['content'], 0, 150);
        $description = properHTML($description);

        mysqli_query($mysql, "UPDATE modx_site_content SET description=$description WHERE id=" . $l['id']);
    }
}

mysqli_free_result($result);
mysqli_close($mysql);

while ($l = mysqli_fetch_assoc($result)) {
    if (empty($l['description']) &&
            !in_array($l['id'], $ignoreIds)
    ) {
        /**
         * strip by number of sentences
         */
        $contents = explode('.', $l['content']);
        $description = $contents[0] . '.' . $contents[1] . '.';

        mysqli_query($mysql, "UPDATE modx_site_content SET description=$description WHERE id=" . $l['id']);
    }
}