I will share with you a class created in PHP used to connect to MySql and also used to perform the necessary operations on the database (Select, Insert, Update e Delete).

Code of PHP class:

class MySQL {
	public $dbCon;
	public function __construct() {
		$this->dbCon = mysqli_connect ( 'URL', 'USER', 'PASSWORD', 'DATABASE_NAME' );
		
		mysqli_query($this->dbCon, 'SET NAMES "utf8";');
		mysqli_query($this->dbCon, 'SET character_set_connection=utf8;');
		mysqli_query($this->dbCon, 'SET character_set_client=utf8;');
		mysqli_query($this->dbCon, 'SET character_set_results=utf8;');
	}
	public function __destruct() {
		mysqli_close ( $this->dbCon );
	}
	
	/*
	 * insert function table name, array value
	 * $values = array('first_name' => 'pramod','last_name'=> 'jain');
	 */
	public function insert($table, $values) {
            $sql = "INSERT INTO $table SET ";
		$c = 0;
		if (! empty ( $values )) {
			foreach ( $values as $key => $val ) {
				if ($c == 0) {
                        $sql .= "$key='".$val."'";
                    }else{
                        $sql .= ", $key='" . $val . "'";
				}
				$c ++;
			}
		} else {
			return false;
		}
		$this->dbCon->query ( $sql ) or die ( mysqli_error () );
		return mysqli_insert_id ( $this->dbCon );
	}
	
	/*
	 * update function table name, array value
	 * $values = array('first_name' => 'pramod','last_name'=> 'jain');
	 * $condition = array('id' =>5,'first_name' => 'pramod!');
	 */
	public function update($table, $values, $condition) {
        $sql="update $table SET ";
		$c = 0;
		if (! empty ( $values )) {
			foreach ( $values as $key => $val ) {
				if ($c == 0) {
                    $sql .= "$key='".$val."'";
                }else{
                    $sql .= ", $key='" . $val . "'";
				}
				$c ++;
			}
		}
		$k = 0;
		if (! empty ( $condition )) {
			foreach ( $condition as $key => $val ) {
				if ($k == 0) {
                    $sql .= " WHERE $key='".$val."'";
                }else{
                    $sql .= " AND $key='" . $val . "'";
				}
				$k ++;
			}
		} else {
			return false;
		}
		$result = $this->dbCon->query ( $sql ) or die ( mysqli_error () );
		return $result;
	}
	
	/*
	 * delete function table name, array value
	 * $where = array('id' =>5,'first_name' => 'pramod');
	 */
	public function delete($table, $where) {
        $sql = "DELETE FROM $table ";
		$k = 0;
		if (! empty ( $where )) {
			foreach ( $where as $key => $val ) {
				if ($k == 0) {
                    $sql .= " where $key='".$val."'";
                }else{
                    $sql .= " AND $key='" . $val . "'";
				}
				$k ++;
			}
		} else {
			return false;
		}
		$del = $result = $this->dbCon->query ( $sql ) or die ( mysqli_error () );
		if ($del) {
			return true;
		} else {
			return false;
		}
	}
	
	/*
	 * select function
	 * $rows = array('id','first_name','last_name');
	 * $where = array('id >' =>5,'first_name =' => 'pramod!');
	 * $order = array('id' => 'DESC','name' => 'ASC');
	 * $limit = array(20,10);
	 */
	public function select($table, $rows = '*', $where = null, $order = null, $limit = null) {
		if ($rows != '*') {
			$rows = implode ( ", ", $rows );
		}

        $sql = 'SELECT '.$rows.' FROM ' . $table;
		if ($where != null) {
			$k = 0;
			foreach ( $where as $key => $val ) {
				if ($k == 0) {
                    $sql .= " where $key '".$val."'";
                }else{
                    $sql .= " AND $key '" . $val . "'";
				}
				$k ++;
			}
		}
		
		$countOrder = 0;
		if ($order != null) {
			$sql .= " ORDER BY ";
			foreach ( $order as $key => $val ) {
                    if($countOrder > 0){
                    	$sql .= ",";
                    }
                    $sql .= " $key " . $val . "";
                    $countOrder++;
			}
		}
		
		if ($limit != null) {
			$limit = implode ( ", ", $limit );
             $sql .= " LIMIT $limit";
		}
		$result = $this->dbCon->query ( urldecode ($sql));
		return $result;
	}
	public function query($sql) {
		$result = $this->dbCon->query ( $sql );
		return $result;
	}
	public function result($result) {
		$row = $result->fetch_array ();
		$result->close ();
		return $row;
	}
	public function row($result) {
		$row = $result->fetch_row ();
		$result->close ();
		return $row;
	}
	public function numrow($result) {
		$row = $result->num_rows;
		$result->close ();
		return $row;
	}
}

Example of a select using the class:

$database = new MySQL ();
$res = $this->con->select ( 'table_name', array (
				'table_field1',
				'table_field2'
		), array (
				'table_field1 = ' => 'Teste1',
				'table_field2 = ' => 'Teste2'
		),array('table_field1' => 'asc',
				'table_field2' => 'desc'
		) );
		
		while ( $query = mysqli_fetch_array ( $res ) ) {				
				echo $query ['table_field1'];				
				echo $query ['table_field2'];
		}