php - 在插入之前检查值，如果已经存在，请不要在php中使用mysql插入它

Question

我有代码检查ips地址（如果重复）将重定向到另一个链接，但是当第一次在表（ip,user_agent,time）中的（click）中插入值时，代码运行良好，但是当我尝试检查是否以某个值运行时它编写了再次在数据库上，我需要任何值（ip,user_agent,time）在数据库上写完之后只写一次，而没有写一些值（ip,user_agent,time）

<?php
    $servername = "localhost";
    $username = "root";
    $password = "rootroot";
    $dbname = "data_clicks";
    //Create connection to database using mysqli
    $conn = new mysqli($servername, $username , $password, $dbname);



    //Set variables according to user input on previous form
    if(isset($_SERVER['REMOTE_ADDR']) && isset($_SERVER['HTTP_USER_AGENT'])){
        $ip = $_SERVER['REMOTE_ADDR'];
        $user = $_SERVER['HTTP_USER_AGENT'];
        $datetime = date_create()->format('d-m-Y ');
    }


    //Define the INSERT statement with IGNORE keyword
        $sql = "INSERT IGNORE INTO clicks (ip, user_agent, time )
        VALUES ('.$ip.', '.$user.', CURRENT_TIMESTAMP)";
        if ($conn->query($sql) === false) {
            die("Database error:".$conn->error);
        }
    // link offer
    $file = "md5.txt";
    $f = fopen($file, 'r');
    $line = fgets($f);
    fclose($f);
    $link="https://facebook.com/?".$line;
    //do smth

    $contents = file($file, FILE_IGNORE_NEW_LINES);
    $first_line = array_shift($contents);
    file_put_contents($file, implode("\r\n", $contents));

    // Check for success
        if ($conn->affected_rows == 0) {
            print "<br>Error! <p></p>";
            echo "" . $ip .''.$user. " already exists in the DCR";
            header("Location: http://www.google.com/");
        } else {

    //Success and return new id
            echo "<br><p></p>Record Added!<p></p>";
            header("Location: $link");
        }
    ?> 

Answer 1

我解决了问题，现在脚本可以正常工作了。

<?php
$servername = "localhost";
$username = "root";
$password = "rootroot";
$dbname = "data_clicks";
//Create connection to database using mysqli
$conn = new mysqli($servername, $username , $password, $dbname);
//Set variables according to user input on previous form
if(isset($_SERVER['REMOTE_ADDR']) && isset($_SERVER['HTTP_USER_AGENT'])){
    $ip = $_SERVER['REMOTE_ADDR'];
    $user = $_SERVER['HTTP_USER_AGENT'];
    $datetime = date_create()->format('d-m-Y ');

}
//Open file md5
$file = "emails/md5.txt";
$f = fopen($file, 'r');
$line = fgets($f);
fclose($f);
$link="https://www.facebook.com/?".$line;
//do smth

$contents = file($file, FILE_IGNORE_NEW_LINES);
$first_line = array_shift($contents);
file_put_contents($file, implode("\r\n", $contents));

//End file md5
// connect mysql


$result = mysqli_query($conn,"SELECT ip FROM clicks WHERE ip='".$ip."'");
$count=mysqli_num_rows($result);

if($count==0)  {
$sql="INSERT INTO clicks (ip, user_agent, time )
VALUES('".$ip."','".$user."', CURRENT_TIMESTAMP)";
if (!mysqli_query($conn,$sql))
{

        }
echo "<br><p></p>Record Added!<p></p>";
        header("Location: $link");
}
else
{ 
    print "<br>Error! <p></p>";
    echo "" . $ip .''.$user. " already exists in the DCR";
    header("Location: http://www.google.com/");
}

//end test
//Define the INSERT statement with IGNORE keyword
    $sql = "INSERT IF NOT EXISTS INTO clicks (ip, user_agent, time )
    VALUES ('$ip', '$user', CURRENT_TIMESTAMP)

)";

// link offer

// Check for success

?>