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POEmpty MySQL query result in PHP
 

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  1. POEmpty MySQL query result in PHP
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    <p>Here's the problematic PHP function:</p> <pre><code>//Get data associated with $criteria from db function getUserData($criteria, $value) { //obtain user data from db based on $criteria=$value global $pdo; //echo $criteria . " " . $value; try { $sql = 'SELECT id, first, last, email, userid FROM users WHERE :criteria= :value'; //var_dump($sql); $st = $pdo-&gt;prepare($sql); $st-&gt;bindValue(':criteria', $criteria); $st-&gt;bindValue(':value', $value); $st-&gt;execute(); } catch (PDOException $ex) { $error = "Failed to obtain user data."; $errorDetails = $ex-&gt;getMessage(); include 'error.html.php'; exit(); } $row = $st-&gt;fetch(); //var_dump($row); if ($row) { $userdata = array(); $userdata['id'] = $row['id']; $userdata['first'] = $row['first']; $userdata['last'] = $row['last']; $userdata['email'] = $row['email']; $userdata['userid'] = $row['userid']; return $userdata; } return FALSE; } </code></pre> <p>I use this function to return a whole row of data associated with specific column in it.</p> <p>When used at it's current state, with a call like that <code>getUserData("email", "John_Stewart_2013")</code>, it returns false, meaning an empty result, while the same query runs fine in MySQL CLI.</p> <p>If I, on the other hand, substitute the query string $sql with :</p> <pre><code>$sql = "SELECT id, first, last, email, userid FROM users WHERE $criteria='$value'"; </code></pre> <p>And comment out the bindValue calls, Every thing runs fine in PHP, and the query returns as desired.</p> <p>But the problem is, those function arguments are user-submitted form data, meaning the solution is vulnerable to SQL Injection.</p> <p>What's wrong here in the first query form?</p>
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    1. CO[Same Q&A here](http://stackoverflow.com/questions/8314043/how-to-dynamically-build-queries-with-pdo)
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