Dediğiniz gibi yapınca aldığım hata şöyledir;

Fatal error: Allowed memory size of 33554432 bytes exhausted (tried to allocate 65484 bytes)

hata aldığımız php dosyasının tamamı şöyledir;

<?php
namespace DB;
final class MySQLi {
private $link;

public function __construct($hostname, $username, $password, $database, $port = '3306') {
$this->link = new mysqli($hostname, $username, $password, $database, $port);

if ($this->link->connect_error) {
trigger_error('Error: Could not make a database link (' . $this->link->connect_errno . ') ' . $this->link->connect_error);
exit();
}

$this->link->set_charset("utf8");
$this->link->query("SET SQL_MODE = ''");
}

public function query($sql) {
$query = $this->link->query($sql);

if (!$this->link->errno) {
if ($query instanceof \mysqli_result) {
$data = array();

while ($row = $query->fetch_assoc()) {
$data[] = $row;
}

$result = new \stdClass();
$result->num_rows = $query->num_rows;
$result->row = isset($data[0]) ? $data[0] : array();
$result->rows = $data;

$query->close();

return $result;
} else {
return true;
}
} else {
trigger_error('Error: ' . $this->link->error . '<br />Error No: ' . $this->link->errno . '<br />' . $sql);
}
}

public function escape($value) {
return $this->link->real_escape_string($value);
}

public function countAffected() {
return $this->link->affected_rows;
}

public function getLastId() {
return $this->link->insert_id;
}

public function __destruct() {
$this->link->close();
}
}

hata alınan kod 7. satırdır yani ;

$this->link = new mysqli($hostname, $username, $password, $database, $port);