如何在 php 中逐行读取文件并将其与现有字符串进行比较？

Question

我试图编写此程序来比较文件中的用户名和输入的用户名以检查它是否存在，但该程序似乎无法运行。请帮忙。该程序应该打开一个名为 allusernames 的文件来比较用户名。如果找不到用户名，请将其添加到文件中。

<?php
    $valid=1;
    $username = $_POST["username"];
    $listofusernames = fopen("allusernames.txt", "r") or die("Unable to open");
    while(!feof($listofusernames)) {
        $cmp = fgets($listofusernames);
        $val = strcmp($cmp , $username);

        if($val == 0) {
            echo ("Choose another user name, the user name you have entered has already been chosen!");
            $valid=0;
            fclose($listofusernames);
            break;
        } else {
            continue;
        }
    }

    if($valid != 0) {
        $finalusers = fopen("allusernames.txt", "a+");
        fwrite($finalusers, $username.PHP_EOL);
        fclose($finalusers);
?>

Answer 1

您需要替换每行中的 linefeed/newline 个字符以进行比较。

while(!feof($listofusernames)) {
    $cmp = fgets($listofusernames);
    $cmp = str_replace(array("\r", "\n"), '',$cmp);
    $val = strcmp($cmp , $username);
    if($val == 0) {
        echo ("Choose another user name, the user name you have entered has already been chosen!");
        $valid=0;
        fclose($listofusernames);
        break;
    } else {
        continue;
    }
}

我在您的代码中添加了以下行

  $cmp = str_replace(array("\r", "\n"), '',$cmp);

Answer 2

你可以用这段代码更简单地做到这一点：

<?php
$username = $_POST["username"];
$listofusernames = 'allusernames.txt';

$content = file($listofusernames);

if(in_array($username, $content)) {
    echo ("Choose another user name, the user name you have entered has already been chosen!");
} else {
    $content[] = $username . PHP_EOL;
    file_put_contents($listofusernames, implode('', $content));
}

?>

Answer 3

我还没有测试过这个，但我想知道你是否可以使用类似

的东西

<?php

$user = $_POST["username"];

$contents = file_get_contents("allusernames.txt");
$usernames = explode("\n",$contents);

if(in_array($user,$usernames))
{
    echo "Choose another username";
}
else
{
    $contents .= "\n".$user;
    file_put_contents("allusernames.txt",$contents);
}

我认为文件获取内容等需要特定版本的 PHP 但它们确实使事情变得更好用。

这还假定您的用户名由新行分隔。

如何在 php 中逐行读取文件并将其与现有字符串进行比较？

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