A wrapper for PHP's MySqli class.

class.db.php

<?php

/* 
** MySQL Abstraction Class
** Allows object creation for DB interaction on more advanced level.
** Objective of this class: Bring exceptions into MySQL errors to provide
** Better error verification and diagnosis.
**
** REQUIREMENTS:
** PHP5 with MySQLi support compiled and configured
** MySQL 4.1 for MySQLi interaction.
*/

/*
** Function to provide more success in variables passed to Class.
** Properly escapes all strings going to the MySQLi functions.
*/

function add_single_quotes($arg)
{
  /* Single quote and escape single quotes and backslashes */
  return "'" . addcslashes($arg, "'\\") . "'";
}

/*
** Function to provide more success in variables passed to class.
** Properly looks at the scalar type of var.
** Returns char type for mysqli_prepare.
**
*/

function getVarType() {

  $type = "";
  $args = func_get_args();
  
  for ($x = 0; $x < count($args); $x++) {

    // If integer, return i
    if (is_int($args[$x])) {
    
      $type .= "i";
    }
    
    // If string, return s
    elseif (is_string($args[$x])) {
    
      $type .= "s";
    }
    
    // If numerical double, return d
    elseif (is_double($args[$x])){
    
      $type .= "d";
    }
    
    // Mysqli->prepare will not allow anything but the above three, except for blob. For blob, manually set.
    else {
    
      die ("Invalid non-scalar value");
    }

  }
      
  return $type;
    
}

/*
** Main Class. Child to main MySQLi class from PHP.
** Usage:
** $var = new DB('hostname', 'username', 'password', 'db');
** All functions are the same as original MySQLi class.
**
** Reminder: To make use of the exceptions, you must connect/query in a TRY block
** and CATCH the type of error.
** 
** Connection Example:
**
** 
** $test = new DB('hostname','username','password','dbname');
**
** Query Example:
**
** $query = "select * from users";
**
** Data Example:
**
** $result = $test->query($query);
**
** print_r($result->fetch_assoc());
**
**
*/

class DB extends mysqli {
  
  function __construct() {

    /* Try to connect, throw exception on error */
    try {
  
      /* Pass all arguments sent to constructor to the parent constructor */
      $args = func_get_args();
      eval("parent::__construct(" . join(',',array_map('add_single_quotes', $args)) . ");");
      
      /* Throw an error if the connection fails */
      if(mysqli_connect_error()) {
        throw new ConnException(mysqli_connect_error(),mysqli_connect_errno());
      }
    }
    
    /*Catch a connection error.*/
    catch (ConnException $exception) {
    
      printf("Connection Error Occurred.\n");
      var_dump($exception->getMessage());
    }
    
    /*Catch any other error*/
    catch (Exception $exception) {
    
      printf("Other Error Occurred.\n");
      var_dump($exception->getMessage());
    }
  }
  
  function query($query) {
    
    /*Attempt the query. Throw exception on error or failure.*/
    try {

      /*Perform a SQL Query utilizing the parent Query function*/
      $result = parent::query($query);
      
      /*Throw an error if the query fails.*/
      if(mysqli_error($this)) {
        throw new QueryException(mysqli_error($this),mysqli_errno($this));
      }
    }
    
    /*Catch any query exception*/
    catch (QueryException $exception) {
      
      printf("Query Error Occurred.\n");
      var_dump($exception->getMessage());
    }
    
    /*Catch any other exception*/
    catch (Exception $exception) {
    
      printf("Other Error Occurred.\n");
      var_dump($exception->getMessage());
    }
    
    return $result;
  }

  function prepare($query) {
    
    $this->stmt = new DBStmt($this, $query);

    return $this->stmt;
  }
}

?>

What's the point of this MySQLi wrapper? MySQLi already can throw excceptions for errors, you just have to turn this on with mysql_report(MSQL_REPORT_ALL).