因此，我花了一些时间研究 MySQLi，但在使用新功能更新脚本时遇到了麻烦。该脚本用于动态下拉表单，使用 JS 发送给它的数据。您可以在此处找到该脚本的实时版本，以查看我正在讨论的内容。我上下查看了我的代码并将其与其他 MySQLi 示例进行了比较，但我不确定我哪里出错了。
现在，第一个下拉菜单甚至没有启动查询，PHP 所做的只是返回预定义的结果，因为它对于第一个选项来说更简单。对我来说，奇怪的是，当它完全不依赖 MySQLi 连接时，即使是第一个下拉菜单现在也不起作用。更新前一切正常，仅供参考。
这是我的脚本：
$db = new mysqli($dbHost, $dbUser, $dbPass, $dbDatabase);
if($db->connect_errno > 0){
die('Unable to connect to database [' . $db->connect_error . ']');
}
//prevents injections
//any order
isset($_GET['type'])?$type = urldecode($_GET['type']):"";
isset($_GET['source'])?$source = $db->real_escape_string(urldecode($_GET['source'])):"";
isset($_GET['range'])?$power = $db->real_escape_string(urldecode($_GET['range'])):"";
isset($_GET['setpoint'])?$setpoint = $db->real_escape_string(urldecode($_GET['setpoint'])):"";
//forms the query depending on what data is recieved through GET
//first option on the bottom; last option on the top to avoid conflicts
if (isset($_GET['setpoint'])) {
$query = "SELECT DISTINCT stp FROM meters WHERE sio='$range' AND pso='$power' AND stp='$setpoint' ORDER BY model";
} elseif (isset($_GET['power'])) {
$query = "SELECT DISTINCT stp FROM meters WHERE sio='$range' AND pso='$power' ORDER BY model";
} elseif (isset($_GET['range'])) {
$query = "SELECT DISTINCT pso FROM meters WHERE sio='$range' ORDER BY model";
} elseif (isset($_GET['source'])) {
$query = "SELECT DISTINCT sir FROM meters WHERE sio LIKE '%$source%' ORDER BY sir";
}
//creates a result array from query results
isset($query)?$result = $db->query($query):"";
//outputs dropdown options dependent on what GET variables are set
//first option on the bottom; last option on the top to avoid conflicts
if (isset($_GET['setpoint'])) {
while ($row = $result->fetch_assoc()) {
echo "<option value='" . $row['stp'] . "'>" . $row['stp'] . "</option>";
$result->free();
}
} elseif (isset($_GET['power'])) {
echo "<option>Please Choose Setpoint Options</option>";
while ($row = $result->fetch_assoc()) {
$row{'stp'} = ucfirst($row{'stp'}); //capitalizes the first letter; necessary?
echo "<option value='" . $row['stp'] . "'>" . $row['stp'] . "</option>";
$result->free();
}
} elseif (isset($_GET['source'])) {
echo "<option>Please Choose Input Range</option>";
while ($row = $result->fetch_assoc()) {
echo "<option value='" . $row['sir'] . "'>" . $row['sir'] . "</option>";
$result->free();
}
} elseif (isset($_GET['type']) && $_GET['type'] == "Digital") {
echo "<option>Please Choose Input Source</option>";
echo "<option value='RS232C'>RS232C</option><option value='RS422'>RS422</option><option value='RS485'>RS485</option><option value='current loop'>current loop</option>";
$result->free();
} elseif (isset($_GET['type']) && $_GET['type'] == "Analog") {
echo "<option>Please Choose Input Source</option>";
echo "<option value='DC current'>DC Current</option><option value='DC voltage'>DC Voltage</option><option value='AC current'>AC Current</option><option value='AC voltage'>AC Voltage</option><option value='process'>Process</option><option value='thermocouple'>Thermocouple</option><option value='RDT'>rdt</option>";
$result->free();
}
编辑：这是我使用过时方法的旧代码。
$con = mysql_connect($dbHost, $dbUser, $dbPass) or trigger_error("Failed to connect to MySQL Server. Error: " . mysql_error());
mysql_select_db($dbDatabase) or trigger_error("Failed to connect to database {$dbDatabase}. Error: " . mysql_error());
//prevents injections
//any order
isset($_GET['type'])?$type = urldecode($_GET['type']):"";
//$type = mysql_real_escape_string(urldecode($_GET['type']));
isset($_GET['source'])?$source = mysql_real_escape_string(urldecode($_GET['source'])):"";
isset($_GET['range'])?$power = mysql_real_escape_string(urldecode($_GET['range'])):"";
isset($_GET['setpoint'])?$setpoint = mysql_real_escape_string(urldecode($_GET['setpoint'])):"";
//forms the query depending on what data is recieved through GET
//first option on the bottom; last option on the top to avoid conflicts
if (isset($_GET['setpoint'])) {
$query = "SELECT DISTINCT stp FROM meters WHERE sio='$range' AND pso='$power' AND stp='$setpoint' ORDER BY model";
} elseif (isset($_GET['power'])) {
$query = "SELECT DISTINCT stp FROM meters WHERE sio='$range' AND pso='$power' ORDER BY model";
} elseif (isset($_GET['range'])) {
$query = "SELECT DISTINCT pso FROM meters WHERE sio='$range' ORDER BY model";
} elseif (isset($_GET['source'])) {
$query = "SELECT DISTINCT sir FROM meters WHERE sio LIKE '%$source%' ORDER BY sir";
}
//creates a result array from query results
isset($query)?$result = mysql_query($query):"";
//outputs dropdown options dependent on what GET variables are set
//first option on the bottom; last option on the top to avoid conflicts
if (isset($_GET['setpoint'])) {
while ($row = mysql_fetch_array($result)) {
echo "<option value='" . $row{'stp'} . "'>" . $row{'stp'} . "</option>";
}
} elseif (isset($_GET['power'])) {
echo "<option>Please Choose Setpoint Options</option>";
while ($row = mysql_fetch_array($result)) {
$row{'stp'} = ucfirst($row{'stp'}); //capitalizes the first letter; necessary?
echo "<option value='" . $row{'stp'} . "'>" . $row{'stp'} . "</option>";
}
} elseif (isset($_GET['source'])) {
echo "<option>Please Choose Input Range</option>";
while ($row = mysql_fetch_array($result)) {
echo "<option value='" . $row{'sir'} . "'>" . $row{'sir'} . "</option>";
}
} elseif (isset($_GET['type']) && $_GET['type'] == "Digital") {
echo "<option>Please Choose Input Source</option>";
echo "<option value='RS232C'>RS232C</option><option value='RS422'>RS422</option><option value='RS485'>RS485</option><option value='current loop'>current loop</option>";
} elseif (isset($_GET['type']) && $_GET['type'] == "Analog") {
echo "<option>Please Choose Input Source</option>";
echo "<option value='DC current'>DC Current</option><option value='DC voltage'>DC Voltage</option><option value='AC current'>AC Current</option><option value='AC voltage'>AC Voltage</option><option value='process'>Process</option><option value='thermocouple'>Thermocouple</option><option value='RDT'>rdt</option>";
}