<?php
# PHP
$dbh = new PDO('mysql:host=localhost;dbname=testdb', 'test', 'test');

$c = pack("CC", 195, 164); # ä

$sql = "insert into test (text) values('$c')";

$sth = $dbh->query($sql);

MariaDB [testdb]> explain test;
+-------+--------------+------+-----+---------+-------+
| Field | Type         | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| id    | int(11)      | YES  |     | NULL    |       |
| text  | varchar(255) | YES  |     | NULL    |       |
+-------+--------------+------+-----+---------+-------+
2 rows in set (0,001 sec)

MariaDB [testdb]> SELECT TABLE_SCHEMA, TABLE_NAME, TABLE_COLLATION FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME = 'test';
+--------------+------------+--------------------+
| TABLE_SCHEMA | TABLE_NAME | TABLE_COLLATION    |
+--------------+------------+--------------------+
| testdb       | test       | utf8mb4_general_ci |
+--------------+------------+--------------------+
1 row in set (0,001 sec)

MariaDB [testdb]> select * from test;
+------+------+
| id   | text |
+------+------+
| NULL | ä    |
+------+------+
1 row in set (0,000 sec)

root@servana:~# php --version
PHP 7.4.33 (cli) (built: Feb 22 2023 20:07:47) ( NTS )
Copyright (c) The PHP Group
Zend Engine v3.4.0, Copyright (c) Zend Technologies
    with Zend OPcache v7.4.33, Copyright (c), by Zend Technologies
root@servana:~#
root@servana:~# mariadb --version
mariadb  Ver 15.1 Distrib 10.5.19-MariaDB, for debian-linux-gnu (x86_64) using  EditLine wrapper
root@servana:~#
root@servana:~# dpkg -l | grep php | grep ii | grep mysql
ii  php-mariadb-mysql-kbs            1.2.12-1                       all          Knowledge base about MariaDB and MySQL server variables
ii  php-mysql                        2:7.4+76                       all          MySQL module for PHP [default]
ii  php7.4-mysql                     7.4.33-1+deb11u3               amd64        MySQL module for PHP
root@servana:~#

…
pdo_mysql

PDO Driver for MySQL => enabled
Client API version => mysqlnd 7.4.33
…

CREATE TABLE `chr` (
  `c` text CHARACTER SET utf8 COLLATE utf8_bin,
  `d` varchar(123) NOT NULL DEFAULT ''
) ENGINE=InnoDB DEFAULT CHARSET=utf8

CREATE TABLE `chr` (
  `c` text CHARACTER SET utf8 COLLATE utf8_bin,
  `d` varchar(123) NOT NULL DEFAULT 'Perl',
  `id` int(11) NOT NULL AUTO_INCREMENT,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=utf8

$VAR1 = [
          {
            'c' => '€',
            'd' => 'Perl',
            'hex(c)' => 'C3A2E2809AC2AC',
            'id' => '1',
            'length(c)' => '7'
          }
        ];