PHP:带变量和不带变量的URI错误

$base_url = "http://example.com/search?";
$query = "keyword=value with spaces";
$url = $base_url . $query; // 错误示例

$base_url = "http://example.com/search?";
$query = "keyword=value with spaces";
$url = $base_url . urlencode($query); // 正确示例

// 假设你有一个表单提交到这个脚本
if (isset($_GET['keyword'])) {
    $keyword = $_GET['keyword'];
    // 处理$keyword
}

<form action="script.php" method="get">
    <input type="text" name="keyword" value="value with spaces">
    <input type="submit" value="Submit">
</form>

$data = array(
    'keyword' => 'value with spaces',
    'page' => 1
);
$query_string = http_build_query($data);
$url = "http://example.com/search?" . $query_string;

$base_url = "http://example.com/search?";
$query_params = array(
    'keyword' => 'value with spaces',
    'page' => 1
);
$query_string = http_build_query($query_params);
$url = $base_url . urlencode($query_string);