CODEWITHSUNDEEP
phppdo
Dycey
Dycey

Reputation: 4685

PHP and PDO dynamic parameter binding

I'm trying to fix this butchered bit of code - as you might have guessed, I'm cocking up the bind param syntax. In fact, I'm not even sure what I'm trying to do is even possible. Here's the class method...

/***
*
* @select values from table
*
* @access public
*
* @param string $table The name of the table
*
* @param array $fieldlist Fields to return in results, defaults null
*
* @param array $criteria Search criteria by keyed by fieldname
*
* @param int $limit Limit of records to return, defaults 10
*
* @return Array on success or throw PDOException on failure
*
*/
public function dbSearch($table, $fieldList = null, $criteria = null, $limit = 10)
{
    // setup $this->db to point to a PDO instance
    $this->conn();

    // build fieldlist
    if( is_null($fieldList) OR !is_array($fieldList) OR count($fieldList) == 0) {
        $returnFields = '*';
    } else {
        $returnFields = "'".implode("', '", $fieldList)."'";
    }

    // build criteria
    if( is_null($criteria) OR !is_array($criteria) OR count($criteria) == 0) {
        $whereClause = '';
    } else {
        $whereClause = array();
        foreach ($criteria as $key => $value){
           $bind_name    = 'bind_'.$key; //generate a name for bind1, bind2, bind3...
           $$bind_name   = $value; //create a variable with this name with value in it
           $bind_names[] = & $$bind_name; //put a link to this variable in array
           $whereClause[] = "'$key' = :$bind_name";
        }
        $whereClause = count($whereClause) > 0 ? ' WHERE '.implode( ' AND ' , $whereClause ) : '';
    }

    $sql = "SELECT $returnFields FROM '$table' $whereClause LIMIT $limit"; 

    $stmt = $this->db->prepare($sql);

    if( $whereClause != '') {
        call_user_func_array(array(&$stmt, 'bindParam'), $bind_names);
    }

    $stmt->execute();
    return $stmt->fetchAll(PDO::FETCH_ASSOC);
}

... which at some point I want to call using something along these lines...

// look for users in database...
$user_recs = $crud->dbSearch('user', array('user_name'), array('user_name'=> $_POST['username']));
$users = $user_recs->fetchAll(PDO::FETCH_ASSOC);

How bonkers is this? Is it possible? Do I need to pass in the param types as well somehow? Any help gratefully received!

Upvotes: 0

Views: 5479

Answers (3)

Dycey
Dycey

Reputation: 4685

Actually, the problem was using bound parameters as opposed to bound values... doh!

Given an SQL statement and some values in an associative array, e.g.

$sql = "SELECT * FROM event
        WHERE eventdate >= :from 
        AND eventdate <= :until 
        AND ( user_name LIKE :st OR site_name LIKE :st )
        ORDER BY eventdate, start_time LIMIT 100";

$values = array( 'st'    => '%'.$searchterm.'%',
                 'from'  => $fromdate,
                 'until' => $untildate, );

then this class method ( but it could easily by a plain function) did the trick:

    public function dbBoundQuery($sql, $values, $types = false) {
        $this->conn();

        $stmt = $this->db->prepare($sql);

        foreach($values as $key => $value) {
            if($types) {
                $stmt->bindValue(":$key",$value,$types[$key]);
            } else {
                if(is_int($value))        { $param = PDO::PARAM_INT; }
                elseif(is_bool($value))   { $param = PDO::PARAM_BOOL; }
                elseif(is_null($value))   { $param = PDO::PARAM_NULL; }
                elseif(is_string($value)) { $param = PDO::PARAM_STR; }
                else { $param = FALSE;}

                if($param) $stmt->bindValue(":$key",$value,$param);
            }
        }

        $stmt->execute();
        return $stmt->fetchAll(PDO::FETCH_ASSOC);
    }

Hope this helps someone else.

Upvotes: 4

Vlad Preda
Vlad Preda

Reputation: 9910

Well, there are quite a few things that can go wrong with the code.

For once, I don't see any AND / OR between WHERE clauses - which is probably why it doesn't work.

Secondly, it doesn't allow you to use SQL functions. Let's say you need to write a query like this:

SELECT * FROM `table` WHERE UNIX_TIMESTAMP(date_added) < ...;

You get the idea.

I would suggest to either use an existing ORM (Doctrine, Propel, etc), or stick to PDO.

Here is an example of how I would use PDO for a User class:

class User
{

 protected $data;
 public function __get($key) {
      return $this->data[$key];
 }
 public function __set($key, $value) {
     $this->data[$key] = $value;
 }
/**
 * @param $value
 * @param $field
 * @return $this
 */
public function loadBy($value, $field)
{
    $db = DbFactory::getInstance();
    $query = "SELECT * FROM users WHERE $field = :$field LIMIT 1";
    $stmt = $db->prepare($query);
    $stmt->execute(array(":$field" => $value));
    $result = $stmt->fetch();

    foreach ($result as $key => $value) {
        $this->$key = $value;
    }

    return $this;
}
}

You can create such functions for your entities, this you will have functions that are specialized, and efficient in what they do, and that are easy to test.

PS: Ignore the issue that appears when you have a field named data :)

Upvotes: 0

Your Common Sense
Your Common Sense

Reputation: 157897

I really don't understand how this function is better than conventional

$stmt = $db->prepare("SELECT user_name FROM user WHERE user_name = ?");
$stmt->execute($_POST['username']);
$users = $stmt->fetchAll();

Mind you,

  • it keeps your query flexible. LIMIT ?,? is possible
  • it keeps your query readable. Almost natural English of SQL stays in place. You still can tell what does your query do, without the need of learning some brain-damaging language. As a side effect, any other developer can comprehend this code too.

Upvotes: 1

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