Complex classes like MySQLi often do a lot of different things. To break such a class down, we need to identify a cohesive component within that class. A common approach to find such a component is to look for fields/methods that share the same prefixes, or suffixes. You can also have a look at the cohesion graph to spot any un-connected, or weakly-connected components.
Once you have determined the fields that belong together, you can apply the Extract Class refactoring. If the component makes sense as a sub-class, Extract Subclass is also a candidate, and is often faster.
While breaking up the class, it is a good idea to analyze how other classes use MySQLi, and based on these observations, apply Extract Interface, too.
| 1 | <?php | ||
| 12 | class MySQLi extends _Abstract { | ||
| 13 | /** | ||
| 14 | * @var \MySQLi Instance of DB connection | ||
| 15 | */ | ||
| 16 | protected $instance; | ||
| 17 | /** | ||
| 18 | * @inheritdoc | ||
| 19 | */ | ||
| 20 | 22 | 	public function __construct ($database, $user = '', $password = '', $host = 'localhost', $prefix = '') { | |
| 21 | 22 | $start = microtime(true); | |
| 22 | /** | ||
| 23 | * Parsing of $host variable, detecting port and persistent connection | ||
| 24 | */ | ||
| 25 | 22 | list($host, $port) = $this->get_host_and_port($host); | |
| 26 | 22 | $this->instance = new \MySQLi($host, $user, $password, $database, $port); | |
| 27 | 22 | 		if (!is_object($this->instance) || $this->instance->connect_errno) { | |
| 28 | 1 | return; | |
| 29 | } | ||
| 30 | 22 | $this->database = $database; | |
| 31 | /** | ||
| 32 | * Changing DB charset if necessary | ||
| 33 | */ | ||
| 34 | 22 | 		if ($this->instance->character_set_name() != 'utf8mb4') { | |
| 35 | 22 | 			$this->instance->set_charset('utf8mb4'); | |
| 36 | } | ||
| 37 | 22 | $this->connected = true; | |
| 38 | 22 | $this->connecting_time = microtime(true) - $start; | |
| 39 | 22 | $this->db_type = 'mysql'; | |
| 40 | 22 | $this->prefix = $prefix; | |
| 41 | 22 | } | |
| 42 | /** | ||
| 43 | * Parse host string into host and port separately | ||
| 44 | * | ||
| 45 | * Understands `p:` prefix for persistent connections | ||
| 46 | * | ||
| 47 | * @param string $host_string | ||
| 48 | * | ||
| 49 | * @return array | ||
| 50 | */ | ||
| 51 | 22 | 	protected function get_host_and_port ($host_string) { | |
| 71 | /** | ||
| 72 | * @inheritdoc | ||
| 73 | * | ||
| 74 | * @return false|mysqli_result | ||
| 75 | */ | ||
| 76 | 22 | 	protected function q_internal ($query, $parameters = []) { | |
| 104 | /** | ||
| 105 | * @inheritdoc | ||
| 106 | * | ||
| 107 | * @param false|mysqli_result $query_result | ||
| 108 | */ | ||
| 109 | 21 | 	public function f ($query_result, $single_column = false, $array = false, $indexed = false) { | |
| 128 | /** | ||
| 129 | * @inheritdoc | ||
| 130 | */ | ||
| 131 | 15 | 	public function id () { | |
| 134 | /** | ||
| 135 | * @inheritdoc | ||
| 136 | */ | ||
| 137 | 1 | 	public function affected () { | |
| 140 | /** | ||
| 141 | * @inheritdoc | ||
| 142 | * | ||
| 143 | * @param false|mysqli_result $query_result | ||
| 144 | */ | ||
| 145 | 18 | 	public function free ($query_result) { | |
| 151 | /** | ||
| 152 | * @inheritdoc | ||
| 153 | */ | ||
| 154 | 2 | 	public function columns ($table, $like = false) { | |
| 166 | /** | ||
| 167 | * @inheritdoc | ||
| 168 | */ | ||
| 169 | 1 | 	public function tables ($like = false) { | |
| 177 | /** | ||
| 178 | * @inheritdoc | ||
| 179 | */ | ||
| 180 | 22 | 	protected function s_internal ($string, $single_quotes_around) { | |
| 184 | /** | ||
| 185 | * @inheritdoc | ||
| 186 | */ | ||
| 187 | 1 | 	public function server () { | |
| 190 | /** | ||
| 191 | * @inheritdoc | ||
| 192 | */ | ||
| 193 | 2 | 	public function __destruct () { | |
| 199 | } | ||
| 200 | 
It seems like the type of the argument is not accepted by the function/method which you are calling.
In some cases, in particular if PHP’s automatic type-juggling kicks in this might be fine. In other cases, however this might be a bug.
We suggest to add an explicit type cast like in the following example: