PHP mysqli

<?php

if (!defined('VALID_ACCESS')) {
    echo -8;
    die('You don\'t belong here!');
}

// Gets called from the form handling code
// $rows is an array containing form data for each new row in the table
// $len is the length of the array
function insertRows($rows, $len) {
    $query = prepareQuery($rows, $len);
    $con = new db('localhost', 'root', 'shibboleet', 'test');
    if (mysqli_connect_errno()) {
        echo -4;
        die('Couldn\'t connect to database! ' . mysqli_connect_error());
    }
    else {
        if (!($stmt = $con->prepare($query))) {
            echo -5;
            die('Couldn\'t connect to database! ' . $con->error);
        }
        bindParams($rows, $len, $stmt);

        if ($stmt->execute()) {
            echo 0;
        }
        else {
            echo -9;
            die('Error: ' . $stmt->error . '<br/>');
        }
        $stmt->close();
    }

    $con->close();
}

// This function prepares the format of the prepared statement by figuring out
// how many rows are to be inserted and how many columns will each row contain.
// Then it just appends the required number of '?' and wraps them in '()'.
// $sepr = ','
// $typeMap contains descriptors for each column of data - 's' or 'i'
// $colMap contains the column names
function prepareQuery($rows, $len) {
    global $base, $sepr, $typeMap, $colMap;
    $str = $base . '(' . implode($sepr, $colMap) . ') VALUES ';
    $entries = 0;
    for ($i = 0; $i < $len; $i++) {
        $toAppend = true;
        $query = '(';

        $tycnt = count($typeMap) - 1;
        $ncols = substr_count($rows[$i], $sepr);
        if ($ncols == $tycnt) {
            for ($j = 0; $j < $ncols; $j++) {
                $query .= '?,';
            }
            $query .= '?';
        }
        else {
            $toAppend = false;
        }

        $query .= ')';
        if ($i < ($len-1)) {
            $query .= ',';
        }

        if ($toAppend) {
            $str .= $query;
            $entries++;
        }
    }
    $str .= ';';

    if ($entries == 0) {
        echo -7;
        die('No valid entries provided!');
    }

    echo $str . '<br/>';
    return $str;
}

// This binds the form data to the prepared statement. The form data is in the format
// <row1_col1>,<row1_col2>,....,<row1_coln>;<row2_col1>,<row2_col2>,...,<row2_coln>;....
// where each <rowi_coli> is base64 encoded.
function bindParams($rows, $len, $stmt) {
    global $sepr, $typeMap;
    for ($i = 0; $i < $len; $i++) {
        $tycnt = count($typeMap);
        $cols = explode($sepr, $rows[$i]);

        if (count($cols) == $tycnt) {
            for ($j =0; $j < $tycnt; $j++) {
                $prm = base64_decode($cols[$j]);
                if ($prm == '') {
                    $prm = NULL;
                }
                $cols[$j] = $prm;
                $stmt->mbind_param($typeMap[$j], $cols[$j]);
            }
        }
    }
}

class db extends mysqli {
    public function prepare($query) {
        return new stmt($this,$query);
    }
}

class stmt extends mysqli_stmt {
    public function __construct($link, $query) {
        $this->mbind_reset();
        parent::__construct($link, $query);
    }

    public function mbind_reset() {
        unset($this->mbind_params);
        unset($this->mbind_types);
        $this->mbind_params = array();
        $this->mbind_types = array('');
    }

    public function mbind_param($type, &$param) {
        $this->mbind_types[0].= $type;
        $this->mbind_params[] = &$param;
    }

    public function mbind_param_do() {
        $params = array_merge($this->mbind_types, $this->mbind_params);
        return  call_user_func_array(array($this, 'bind_param'),
                $this->makeValuesReferenced($params));
    }

    private function makeValuesReferenced($arr){
        $refs = array();
        foreach($arr as $key => $value) {
            $refs[$key] = &$arr[$key];
        }
        return $refs;
    }

    public function execute() {
        if(count($this->mbind_params)) {
            if (!$this->mbind_param_do()) {
                echo -11;
                die('Error binding parameters! ' . $this->error . '<br/>');
            }
        }
        return parent::execute();
    }

    private $mbind_types = array('');
    private $mbind_params = array();
}

?>