How to support emojis with flourish?

I am using flourishlib for a website. My client requested that we should be able to use emojis with mobile phones. In theory we should change the character-encoding from utf8 to utf8mb4 for the MySQL database.

So far, so good, however, if we make this switch, like this:

# For each database:
ALTER DATABASE database_name CHARACTER SET = utf8mb4 COLLATE utf8mb4_unicode_ci;
# For each table:
ALTER TABLE table_name CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
# For each column:
ALTER TABLE table_name CHANGE column_name column_name VARCHAR(191) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
# (Don’t blindly copy-paste this! The exact statement depends on the column type, maximum length, and other properties. The above line is just an example for a `VARCHAR` column.)

Then each character will use four bytes instead of three bytes. This would increase the database's size with 33%. This would result in worse performance and more storage space used up. So, as a result, we have decided to switch to an encoding of utf8mb4 for only specific columns of specific tables.

To make sure everything is all right, I have checked several things. Among them, I have checked flourishlib and found a few suspect parts:

There is an fUTF8 class, which does not seem to support utf8mb4

At fDatabase I am quoting some findings:

if ($this->connection && function_exists('mysql_set_charset') && !mysql_set_charset('utf8', $this->connection)) {
    throw new fConnectivityException(
        'There was an error setting the database connection to use UTF-8'
    );
}
//...
// Make MySQL act more strict and use UTF-8
if ($this->type == 'mysql') {
    $this->execute("SET SQL_MODE = 'REAL_AS_FLOAT,PIPES_AS_CONCAT,ANSI_QUOTES,IGNORE_SPACE'");
    $this->execute("SET NAMES 'utf8'");
    $this->execute("SET CHARACTER SET utf8");
}

At fSQLSchemaTranslation I can see this:

$sql = preg_replace('#\)\s*;?\s*$#D', ')ENGINE=InnoDB, CHARACTER SET utf8', $sql);

I have the suspicion that flourishlib will not support our quest of making a few columns of a few table have a character encoding of utf8mb4. I wonder whether we can upgrade something somehow to make this support. As a worst-case scenario, we can override every textual occurrence of utf8 to utf8mb4. However, that would be a very ugly hack and we wonder whether there is a better solution. Should we make this hack or is there a more orthodox approach?

Solution

I have resolved the issue. I have altered the tables where I wanted to support emojis by changing the column character set and collation, like this:

ALTER TABLE table_name CHANGE column_name column_name text CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;

After that, I had to make a few ugly hacks to make flourishlib able to support emojis.

fDatabase.php:

line 685:

        if ($this->connection && function_exists('mysql_set_charset') && !mysql_set_charset('utf8mb4', $this->connection)) {
            throw new fConnectivityException(
                'There was an error setting the database connection to use UTF-8'
            );
        }

line 717 stays the same, everything crashes if this line is changed:

if ($this->connection && function_exists('mysqli_set_charset') && !mysqli_set_charset($this->connection, 'utf8')) {

line 800:

    // Make MySQL act more strict and use UTF-8
    if ($this->type == 'mysql') {
        $this->execute("SET SQL_MODE = 'REAL_AS_FLOAT,PIPES_AS_CONCAT,ANSI_QUOTES,IGNORE_SPACE'");
        $this->execute("SET NAMES 'utf8mb4'");
        $this->execute("SET CHARACTER SET utf8mb4");
    }

fSQLSchemaTranslation.php:

line 1554:

$sql = preg_replace('#\)\s*;?\s*$#D', ')ENGINE=InnoDB, CHARACTER SET utf8mb4', $sql);

fXML.php:

line 403:

    if (preg_replace('#[^a-z0-9]#', '', strtolower($encoding)) == 'utf8mb4') {
        // Remove the UTF-8 BOM if present
        $xml = preg_replace("#^\xEF\xBB\xBF#", '', $xml);
        fCore::startErrorCapture(E_NOTICE);
        $cleaned = self::iconv('UTF-8', 'UTF-8', $xml);
        if ($cleaned != $xml) {
            $xml = self::iconv('Windows-1252', 'UTF-8', $xml);
        }
        fCore::stopErrorCapture();
    }

and finally, when there are modifications for any of the columns affected, I execute this:

App::db()->query("set names 'utf8mb4'");

which, essentially triggers the ->query() execution of an fDatabase object.