PHP函数查询数据库如何操作

在PHP中，我们可以使用MySQLi和PDO两种方式连接和操作数据库。

1. 连接数据库

MySQLi连接数据库方式：

//连接数据库
$mysqli = new mysqli("localhost", "username", "password", "databaseName");
if ($mysqli->connect_errno) {
    die("连接失败：" .$mysqli->connect_error);
}

PDO连接数据库方式：

//连接数据库
try {
    $pdo = new PDO("mysql:host=localhost;dbname=databaseName", "username", "password");
    $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
} catch (PDOException $e) {
    echo "连接失败：" .$e->getMessage();
    exit();
}

2. 查询数据

MySQLi查询数据方式：

//查询数据
$sql = "SELECT column1, column2, column3 FROM tableName";
$result = $mysqli->query($sql);

if ($result->num_rows > 0) {
    while ($row = $result->fetch_assoc()) {
        echo "column1: " .$row["column1"]. " - column2: " .$row["column2"]. " - column3: " .$row["column3"];
    }
} else {
    echo "0 结果";
}

PDO查询数据方式：

//查询数据
$sql = "SELECT column1, column2, column3 FROM tableName";
$stmt = $pdo->prepare($sql);
$stmt->execute();

if ($stmt->rowCount() > 0) {
    while ($row = $stmt->fetch(PDO::FETCH_ASSOC)) {
        echo "column1: " .$row["column1"]. " - column2: " .$row["column2"]. " - column3: " .$row["column3"];
    }
} else {
    echo "0 结果";
}

3. 插入数据

MySQLi插入数据方式：

//插入数据
$sql = "INSERT INTO tableName (column1, column2, column3) VALUES ('value1', 'value2', 'value3')";
if ($mysqli->query($sql) === TRUE) {
    echo "插入成功";
} else {
    echo "错误：" .$mysqli->error;
}

PDO插入数据方式：

//插入数据
$sql = "INSERT INTO tableName (column1, column2, column3) VALUES (:value1, :value2, :value3)";
$stmt = $pdo->prepare($sql);
$stmt->bindParam(':value1', $value1);
$stmt->bindParam(':value2', $value2);
$stmt->bindParam(':value3', $value3);

$value1 = 'value1';
$value2 = 'value2';
$value3 = 'value3';

if ($stmt->execute()) {
    echo "插入成功";
} else {
    echo "错误：" .$stmt->errorInfo()[2];
}

4. 更新数据

MySQLi更新数据方式：

//更新数据
$sql = "UPDATE tableName SET column1='value1', column2='value2', column3='value3' WHERE id=1";
if ($mysqli->query($sql) === TRUE) {
    echo "更新成功";
} else {
    echo "错误：" .$mysqli->error;
}

PDO更新数据方式：

//更新数据
$sql = "UPDATE tableName SET column1=:value1, column2=:value2, column3=:value3 WHERE id=1";
$stmt = $pdo->prepare($sql);
$stmt->bindParam(':value1', $value1);
$stmt->bindParam(':value2', $value2);
$stmt->bindParam(':value3', $value3);

$value1 = 'value1';
$value2 = 'value2';
$value3 = 'value3';

if ($stmt->execute()) {
    echo "更新成功";
} else {
    echo "错误：" .$stmt->errorInfo()[2];
}

5. 删除数据

MySQLi删除数据方式：

//删除数据
$sql = "DELETE FROM tableName WHERE id=1";
if ($mysqli->query($sql) === TRUE) {
    echo "删除成功";
} else {
    echo "错误：" .$mysqli->error;
}

PDO删除数据方式：

//删除数据
$sql = "DELETE FROM tableName WHERE id=1";
$stmt = $pdo->prepare($sql);

if ($stmt->execute()) {
    echo "删除成功";
} else {
    echo "错误：" .$stmt->errorInfo()[2];
}

以上就是一个简单的PHP函数查询数据库操作的流程，在实际开发中，我们需要根据不同的需求来进行适当的修改和优化。