How to echo a MySQLi prepared statement?

user_115681 0
Viewed 58313

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.

mysqli php
6 Answers

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')
user_703930

Just set it to die and output the last executed query. The Error handling should give you meaningful information which you can use to fix up your query.

user_1189760

You can turn on log queries on mysql server. Just execute command: 

sql> SHOW VARIABLES LIKE "general_log%";
sql> SET GLOBAL general_log = 'ON';

And watch queries in the log file. After testing turn log off:

sql> SET GLOBAL general_log = 'OFF';
user_62488820

I was able to use var_dump() to at least get a little more info on the mysqli_stmt:

  $postmeta_sql = "INSERT INTO $db_new.wp_postmeta (post_id, meta_key, meta_value) VALUES (?, ?, ?)";
  $stmt = $new_conn->prepare($postmeta_sql);
  $stmt->bind_param("sss", $post_id, $meta_key, $meta_value);
  echo var_dump($stmt);
  $stmt->execute();
  $stmt->close();
user_121495290
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