PDO-从“选择”语句显示行

Question

I have been struggling for a while to get the following code to run, it isnt returning anything:

try {
  $DBH = new PDO("mysql:host=$dbHost;dbname=$dbDatabase", $dbUser, $dbPass);
  $DBH->setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION );
  $STH = $DBH->prepare('SELECT * FROM `component`');
  # setting the fetch mode
  $STH->setFetchMode(PDO::FETCH_ASSOC);

  while($row = $STH->fetchAll()) {
    echo $row['cid'] . "\n";
    echo $row['cdesc'] . "\n";
    echo $row['cinfo'] . "\n";
  }
}
catch(PDOException $e) {
  echo "I'm sorry. I'm afraid I can't do that.";
  echo $e->getMessage();
}

Any assistance would be appreciated. Rgds, Stew

Answer 1

fetchAll returns all the rows, if you want to iterate over the results you can use fetch :

while($row = $STH->fetch())

Or if you want to stick with fetchAll() :

$rows = $STH->fetchAll();
foreach($row in $rows){
  ...
}

As bitWorking pointed out you are also missing the call to execute :

$STH = $DBH->prepare('SELECT * FROM `component`');
$STH->execute();
# setting the fetch mode
$STH->setFetchMode(PDO::FETCH_ASSOC);

Answer 2

You missed the execute method. Also wrong usage of fetchAll.

See Example #1 Fetch all remaining rows in a result set

Another example with fetchMode:

$STH = $DBH->prepare('SELECT * FROM `component`');
$STH->execute();
$STH->setFetchMode(PDO::FETCH_ASSOC);

// since PDOStatement implements Traversable you can directly iterate
foreach ($STH as $row) {
    echo $row['cid'] . "\n";
}