常见的PHP内置对象大全：掌握常用内置对象的了解

$str = "Hello World";
$str_length = strlen($str); // 获取字符串长度
$str_upper = strtoupper($str); // 将字符串转为大写
$str_lower = strtolower($str); // 将字符串转为小写

echo "字符串长度：".$str_length."
";
echo "大写字符串：".$str_upper."
";
echo "小写字符串：".$str_lower."
";

$fruits = array("Apple", "Banana", "Orange");

$fruits_count = count($fruits); // 获取数组长度
$fruits_sort = sort($fruits); // 对数组进行排序

echo "水果个数：".$fruits_count."
";
echo "排序后的水果：";
print_r($fruits);

$file_path = "demo.txt";
$file_handle = fopen($file_path, "r"); // 打开文件

$file_content = fread($file_handle, filesize($file_path)); // 读取文件内容

fclose($file_handle); // 关闭文件

echo "文件内容：".$file_content."
";

$current_time = time(); // 获取当前时间戳

$date_format = date("Y-m-d H:i:s", $current_time); // 格式化时间

echo "当前时间：".$date_format."
";

$str = "Hello World";

$pattern = "/Ww+/"; // 匹配以W开头的单词

$matches = array();
preg_match($pattern, $str, $matches); // 进行匹配

echo "匹配结果：";
print_r($matches);