php-doc-en/reference/mysqli/examples.xml

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<chapter xml:id="mysqli.examples" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
 &reftitle.examples;
 <section xml:id="mysqli.examples-basic">
  <title>MySQLi extension basic examples</title>
  <para>
   This example shows how to connect, execute a query, use basic
   error handling, print resulting rows, and disconnect from a MySQL database.
  </para>
  <para>
   This example uses the freely available Sakila database that
   can be downloaded from <link xlink:href="&url.mysql.sakila;">dev.mysql.com,
   as described here</link>. To get this example to work, (a) install sakila 
   and (b) modify the connection variables (host, your_user, your_pass).
  </para>
  <example>
   <title>MySQLi extension overview example</title>
   <programlisting role="php">
<![CDATA[
<?php
// Let's pass in a $_GET variable to our example, in this case
// it's aid for actor_id in our Sakila database. Let's make it
// default to 1, and cast it to an integer as to avoid SQL injection
// and/or related security problems. Handling all of this goes beyond
// the scope of this simple example. Example:
//   http://example.org/script.php?aid=42
if (isset($_GET['aid']) && is_numeric($_GET['aid'])) {
    $aid = (int) $_GET['aid'];
} else {
    $aid = 1;
}

// Connecting to and selecting a MySQL database named sakila
// Hostname: 127.0.0.1, username: your_user, password: your_pass, db: sakila
$mysqli = new mysqli('127.0.0.1', 'your_user', 'your_pass', 'sakila');

// Oh no! A connect_errno exists so the connection attempt failed!
if ($mysqli->connect_errno) {
    // The connection failed. What do you want to do? 
    // You could contact yourself (email?), log the error, show a nice page, etc.
    // You do not want to reveal sensitive information

    // Let's try this:
    echo "Sorry, this website is experiencing problems.";

    // Something you should not do on a public site, but this example will show you
    // anyways, is print out MySQL error related information -- you might log this
    echo "Error: Failed to make a MySQL connection, here is why: \n";
    echo "Errno: " . $mysqli->connect_errno . "\n";
    echo "Error: " . $mysqli->connect_error . "\n";
    
    // You might want to show them something nice, but we will simply exit
    exit;
}

// Perform an SQL query
$sql = "SELECT actor_id, first_name, last_name FROM actor WHERE actor_id = $aid";
if (!$result = $mysqli->query($sql)) {
    // Oh no! The query failed. 
    echo "Sorry, the website is experiencing problems.";

    // Again, do not do this on a public site, but we'll show you how
    // to get the error information
    echo "Error: Our query failed to execute and here is why: \n";
    echo "Query: " . $sql . "\n";
    echo "Errno: " . $mysqli->errno . "\n";
    echo "Error: " . $mysqli->error . "\n";
    exit;
}

// Phew, we made it. We know our MySQL connection and query 
// succeeded, but do we have a result?
if ($result->num_rows === 0) {
    // Oh, no rows! Sometimes that's expected and okay, sometimes
    // it is not. You decide. In this case, maybe actor_id was too
    // large? 
    echo "We could not find a match for ID $aid, sorry about that. Please try again.";
    exit;
}

// Now, we know only one result will exist in this example so let's 
// fetch it into an associated array where the array's keys are the 
// table's column names
$actor = $result->fetch_assoc();
echo "Sometimes I see " . $actor['first_name'] . " " . $actor['last_name'] . " on TV.";

// Now, let's fetch five random actors and output their names to a list.
// We'll add less error handling here as you can do that on your own now
$sql = "SELECT actor_id, first_name, last_name FROM actor ORDER BY rand() LIMIT 5";
if (!$result = $mysqli->query($sql)) {
    echo "Sorry, the website is experiencing problems.";
    exit;
}

// Print our 5 random actors in a list, and link to each actor
echo "<ul>\n";
while ($actor = $result->fetch_assoc()) {
    echo "<li><a href='" . $_SERVER['SCRIPT_FILENAME'] . "?aid=" . $actor['actor_id'] . "'>\n";
    echo $actor['first_name'] . ' ' . $actor['last_name'];
    echo "</a></li>\n";
}
echo "</ul>\n";

// The script will automatically free the result and close the MySQL
// connection when it exits, but let's just do it anyways
$result->free();
$mysqli->close();
?>
]]>
   </programlisting>
  </example>
 </section>
</chapter>

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