$str = "Hello World";
echo lcfirst($str); // 输出：hello World
$str = "Hello World";
$firstWord = lcfirst(substr($str, 0, strpos($str, ' ')));
echo $firstWord . substr($str, strpos($str, ' ')); // 输出：hello World
$array = ["Apple", "Banana", "Cherry"];
$newArray = array_map('lcfirst', $array);
print_r($newArray); // 输出：Array ( [0] => apple [1] => banana [2] => cherry )
