How to represent a PHP array as a comma-delimited string? [duplicate]

Answer 1

Use implode();

$ids = implode(',', $your_array);

Answer 2

If you're using PDO or mysqli (which you should, as the mysql_ functions are antiquated and should be abandoned), then you'll want to construct a parameterized query using the number of elements in your array to match the number of ?'s in your SQL.

Here's an example in PDO:

$ids = array(1, 2, 3, 4);

try {
    $dbh = new PDO("mysql:host=localhost;dbname=mydbname", 'username', 'password');
} catch(PDOException $e) {
    die($e->getMessage());
}

$inClause = trim(str_repeat('?, ', count($ids)), ', ');
$stm = $dbh->prepare('SELECT * FROM mytable WHERE id IN ('.$inClause.')');
$stm->execute($ids);

// resulting SQL: SELECT * FROM mytable WHERE id IN (?, ?, ?, ?)