How to echo a MySQLi prepared statement?

I'm playing around with MySQLi at the moment, trying to figure out how it all works. In my current projects I always like to echo out a query string while coding, just to make sure that everything is correct, and to quickly debug my code. But... how can I do this with a prepared MySQLi statement?

Example:

$id = 1;
$baz = 'something';

if ($stmt = $mysqli->prepare("SELECT foo FROM bar WHERE id=? AND baz=?")) {
  $stmt->bind_param('is',$id,$baz);
  // how to preview this prepared query before acutally executing it?
  // $stmt->execute();
}

I've been going through this list (http://www.php.net/mysqli) but without any luck.

EDIT

Well, if it's not possible from within MySQLi, maybe I'll stick with something like this:

function preparedQuery($sql,$params) {
  for ($i=0; $i<count($params); $i++) {
    $sql = preg_replace('/\?/',$params[$i],$sql,1);
  }
  return $sql;
}

$id = 1;
$baz = 'something';

$sql = "SELECT foo FROM bar WHERE id=? AND baz=?";

echo preparedQuery($sql,array($id,$baz));

// outputs: SELECT foo FROM bar WHERE id=1 AND baz=something

Far from perfect obviously, since it's still pretty redundant — something I wanted to prevent — and it also doesn't give me an idea as to what's being done with the data by MySQLi. But I guess this way I can quickly see if all the data is present and in the right place, and it'll save me some time compared to fitting in the variables manually into the query — that can be a pain with many vars.

I don't think you can - at least not in the way that you were hoping for. You would either have to build the query string yourself and execute it (ie without using a statement), or seek out or create a wrapper that supports that functionality. The one I use is Zend_Db, and this is how I would do it:

$id = 5;
$baz = 'shazam';
$select = $db->select()->from('bar','foo')
                       ->where('id = ?', $id)
                       ->where('baz = ?', $baz); // Zend_Db_Select will properly quote stuff for you
print_r($select->__toString()); // prints SELECT `bar`.`foo` FROM `bar` WHERE (id = 5) AND (baz = 'shazam')

I have struggled with this one in the past. So to get round it I wrote a little function to build the SQL for me based on the SQL, flags and variables.

//////////// Test Data //////////////
$_GET['filmID'] = 232;
$_GET['filmName'] = "Titanic";
$_GET['filmPrice'] = 10.99;

//////////// Helper Function //////////////
function debug_bind_param(){
    $numargs = func_num_args();
    $numVars = $numargs - 2;
    $arg2 = func_get_arg(1);
    $flagsAr = str_split($arg2);
    $showAr = array();
    for($i=0;$i<$numargs;$i++){
        switch($flagsAr[$i]){
        case 's' :  $showAr[] = "'".func_get_arg($i+2)."'";
        break;
        case 'i' :  $showAr[] = func_get_arg($i+2);
        break;  
        case 'd' :  $showAr[] = func_get_arg($i+2);
        break;  
        case 'b' :  $showAr[] = "'".func_get_arg($i+2)."'";
        break;  
        }
    }
    $query = func_get_arg(0);
    $querysAr = str_split($query);
    $lengthQuery = count($querysAr);
    $j = 0;
    $display = "";
    for($i=0;$i<$lengthQuery;$i++){
        if($querysAr[$i] === '?'){
            $display .= $showAr[$j];
            $j++;   
        }else{
            $display .= $querysAr[$i];
        }
    }
    if($j != $numVars){
        $display = "Mismatch on Variables to Placeholders (?)"; 
    }
    return $display;
}

//////////// Test and echo return //////////////

echo debug_bind_param("SELECT filmName FROM movies WHERE filmID = ? AND filmName = ? AND price = ?", "isd", $_GET['filmID'], $_GET['filmName'], $_GET['filmPrice']);

I have also build a little online tool to help.

Mysqli Prepare Statement Checker

How to echo a MySQLi prepared statement?

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