A helper class to build prepared statements using WordPress's WPDB class.

QueryBuilder.php

<?php

/**
 * A helper class to allow you to easily build prepared statements
 * for use with Wordpress's WPDB class.
 *
 * Usage: $this->orderBy('column', 'asc')->limit(50)->getQuery();
 */
 class QueryBuilder {

    /**
     * Table name to select rows from.
     * @var string
     */
    private $table;

    /**
     * Associative array, usually $_GET vars.
     * @var array
     */
    private $params;

    /**
     * A string for a SQL LIMIT
     * @var mixed
     */
    private $limit;

    /**
     * A string for SQL ORDER BY
     * @var mixed
     */
    private $orderBy;


    function __construct($table, array $params)
    {
        $this->table = $table;
        $this->params = $params;
    }

    /**
     * Returns the prepared statement.
     * @return string
     */
    public function getQuery()
    {
        return $this->buildQuery();
    }

    /**
     * Build a prepared SQL statement using WordPress's WPDB class.
     *
     * @return string
     */
    private function buildQuery()
    {
        global $wpdb;

        foreach ($this->params as $key => $value) {
            $format = is_numeric($value) ? '%d' : '%s';
            $sql[] = " `$key` = $format";
            $values[] = $value;
        }

        return $wpdb->prepare(
            "SELECT * FROM `{$this->table}` ".
            "WHERE " . implode(' AND ', $sql).
            $this->limit .
            $this->orderBy
            , $values);
    }

    /**
     * Set a SQL LIMIT on the query string.
     *
     * @param $limit
     * @return QueryBuilder
     */
    public function limit($limit)
    {
        $this->limit = ' LIMIT '. intval($limit);
        return $this;
    }

    /**
     * Set column to order results by
     *
     * @param string $orderBy DB Column
     * @param string $order Sort Order
     * @return $this
     */
    public function orderBy($orderBy, $order = 'ASC')
    {
        $this->orderBy = ' ORDER BY `'. $orderBy .'` '.$order;
        return $this;
    }

}

I built this for a small plugin I wrote that had a bunch of selects that allowed users to filter data using $_GET variables. I didn't want to do a bunch of if / else statements so I wrote this class so I could do something like

$builder = new QueryBuilder($table, $_GET)
$query = $builder->getQuery();

without the need to use a bunch of $wpdb->prepare() statements you can now use this class with any FLAT associative array.

I expect to modify this in the future but for now I figured it fit my needs for the time being.

@bgallagh3r I stumbled on this through some Googling and just wanted to point out that I think this is susceptible to SQL injection if you use it as described (passing $_GET) because the keys are not escaped.