获取数据表的全部信息并返回json编码

<?php
    $host = "127.0.0.1";   // 服务器地址
    $username = "root";   // 用户名
    $password = "";  // 密码
    $databaseName = "raceinfo";  // 数据库名

    // 进行查询操作的sql语句
	$query = "select * from runners";

    // 连接数据库
	$conn = db_connection($host, $username, $password, $databaseName);
    // 执行查询操作
	$result = mysqli_query($conn, $query);

    // 创建一个空数组，为转换成json格式而准备
	$runners = array();

    // 遍历查询得到的每条记录
    while($row = mysqli_fetch_array($result, MYSQL_ASSOC)){
        // print_r($row);
        // echo "<br>";
        // 把当前记录放到$runners数组中，数组中的每一个元素也是一个数组
        array_push($runners, array("fname" => $row["first_name"]));
    }

    echo json_encode(array("runners" => $runners));

    // 该函数的作用是连接数据库，如果连接成功返回连接对象，否则输出错误提示信息，结束该php文件的运行
    function db_connection($host, $username, $password, $databaseName){
        $conn = mysqli_connect($host, $username, $password, $databaseName);
        if (!$conn) {
            die("Could not connect to database: " . mysqli_connect_errno());
        }
        return $conn; // 返回连接对象
    }
?>

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根据分页返回页面数量或者当前页信息

<?php 
	if(isset($_POST["index"])){
  		$pageIndex = $_POST["index"];
	}
	if(isset($_POST["size"])){
  		$pageSize = $_POST["size"];
	}

	$host = "127.0.0.1";   // 服务器地址
    $username = "root";   // 用户名
    $password = "";  // 密码
    $databaseName = "raceinfo";  // 数据库名

	// 首次查询，只需要得到记录数量即可
	if($pageIndex==0){
		$query = "select count(*) from runners";
		// 连接数据库
		$conn = db_connection($host, $username, $password, $databaseName);
		// 执行查询操作
		$result = $conn->query($query);

		echo json_encode(array("total"=>mysqli_fetch_array($result)['0']));
	}
	else{
		// 设置偏移记录数，即设置开始行号
		$startRowNum = ($pageIndex-1) * $pageSize;  
		$numOfRows = $pageSize;  // 返回的最多行数
		$query = "select * from runners order by runner_id asc limit ".$startRowNum.",". $numOfRows;

		// 连接数据库
		$conn = db_connection($host, $username, $password, $databaseName);
		// 执行查询操作
		$result = $conn->query($query);

		$runners = array();
		while($row = mysqli_fetch_array($result)){
	        array_push($runners, $row);
		}

		echo json_encode($runners);
	}

	function db_connection($host, $username, $password, $databaseName){
        $conn = mysqli_connect($host, $username, $password, $databaseName);
        // 下面两条语句用来防止中文乱码
    	mysqli_query($conn,"set character set 'utf8'");
		mysqli_query($conn,"set names 'utf8'");
        if (mysqli_connect_errno()) {
     		echo "Could not connect to database.";
     		exit();
        }
        return $conn; // 返回连接对象
    }
 ?>