SQL PHP插入命令

Question

<?php
$con=mysqli_connect("example.com","peter","abc123","my_db");

// Check connection
if (mysqli_connect_errno())
{
    echo "Failed to connect to MySQL: " . mysqli_connect_error();
}

$sql="INSERT INTO Persons (FirstName, LastName, Age)
VALUES
('$_POST[firstname]','$_POST[lastname]','$_POST[age]')";

if (!mysqli_query($con,$sql))
{
    die('Error: ' . mysqli_error($con));
}

echo "1 record added";

mysqli_close($con);
?>

上面的代码正确执行但我不明白如何在不编写mysqli_query($ sql)的情况下执行变量$ sql？

Answer 1

它在行中执行:

   if (!mysqli_query($con,$sql))

换句话说,"if"检查mysqli_query的结果,所以要做到这一点,它必须执行它.