php undefined index with isset $_POST

Question

trying to create a chat and keep getting Undefined index i've tried adding ? $_POST['chat'] : null; but doesn't work

Notice: Undefined index: chat in /Applications/MAMP/htdocs/chat/chat.php on line 8

Line 8:

$sent = $_POST['chat'];

the variable is used here:

if (isset($_POST['chat'])) {
    if (!empty($sent)) {
        fwrite($myfile, $first.': '.$txt.'=');
        fclose($myfile);
    } else if (empty($sent)) {
        if(isset($_POST['chat'])){
            echo 'Cant send an empty message','<br />';
        }
    }
}

HTML:

<body>
    <iframe id='reload' src='refresh.php'>
        <fieldset class="field">
                <div id="list"><p><?php
                    $filename = 'chat.txt';
                    $handle = fopen($filename, 'r');

                    $detain = fread($handle, filesize($filename));

                    $chat_array = explode('=', $detain);

                    foreach($chat_array as $chat) {
                        echo $chat.'<br />';
                    }
                    ?></p></div>
        </fieldset>
    </iframe>
    <form action="chat.php" method="POST">
        <input type="text" name="chat" class="textbox">
        <input type="submit" value="Send" class="button">
    </form>
</body>

Variables:

    $sent = $_POST['chat'];
    $myfile = fopen("chat.txt", 'a') or die("Unable to open file!");
    $txt = ($sent."\n");
    $first = getuserfield('username');
    $active = ($first.":".$ip_addr);
    $activef = fopen("ip-user.txt", 'a');
    $myFile = "domains/domain_list.txt";

Edit: This is not a duplicate because this is for a very specific piece of code, i've also already used empty and I would not like to ignore the problem because it is a possible cause of another problem.

Thank you.

Possible duplicate of PHP: "Notice: Undefined variable" and "Notice: Undefined index" — Narendrasingh Sisodia
– Narendrasingh Sisodia, Commented Apr 30, 2016 at 5:26

Manjeet Barnala · Accepted Answer · 2016-04-30 05:56:00Z

1

Use this code :

<?php 
$sent = '';
if(isset($_POST['chat'])) 
{
    $sent = $_POST['chat'];
    if (!empty($sent))
    {
        $txt = ($sent."\n");
        fwrite($myfile, $first.': '.$txt.'=');
        fclose($myfile);
    } 
    else 
    {
        echo 'Cant send an empty message','<br />';
    }
}
?>

edited Apr 30, 2016 at 5:56

answered Apr 30, 2016 at 5:41

Manjeet Barnala

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5 Comments

jane boe Over a year ago

that removes the error but the then no text is submitted

Manjeet Barnala Over a year ago

where is your $txt coming from ??

jane boe Over a year ago

the text is coming from $sent

Manjeet Barnala Over a year ago

use $txt = ($sent."\n"); inside not empty $send condition

Manjeet Barnala Over a year ago

great!!.. Thank You for appreciation.. @janeboe

Dave Ross · Accepted Answer · 2016-04-30 05:40:08Z

1

You said you tried a ternary conditional, but didn't post an example of what you tried. It should look like this:

$sent = isset($_POST['chat']) ? $_POST['chat'] : null;

In PHP 7.0 or higher, you can simplify this expression with the null coalesce operator:

$sent = $_POST['chat'] ?? null;

answered Apr 30, 2016 at 5:40

Dave Ross

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Comments

SonDang · Accepted Answer · 2016-04-30 05:30:49Z

0

did you submit the form ?

PHP:

if (isset($_POST['chat'])) {
if (!empty($sent)) {
    fwrite($myfile, $first.': '.$txt.'=');
    fclose($myfile);
} else if (empty($sent)) {
    if(isset($_POST['chat'])){
        echo 'Cant send an empty message','<br />';
    }
}

}

HTML:

<form action="" method="POST">
    <input type="text" name="chat">
    <input type="submit" name="submit">
</form>

answered Apr 30, 2016 at 5:30

SonDang

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1 Comment

SonDang Over a year ago

the code works fine in my environment, can you post your html code to the question? Also, try with another name beside chat.

Pinke Helga · Accepted Answer · 2016-04-30 05:48:32Z

0

Do something like $sent = isset($_POST['chat']) ? $_POST['chat'] : '';

btw.: There is much redundance in you code.

if (isset($_POST['chat'])) {
  if (!empty($sent)) {
    fwrite($myfile, $first.': '.$txt.'=');
    fclose($myfile);
  } else {
    echo 'Cant send an empty message','<br />';
  }
}

If you don't want to write an isset() condition every time, you could define a short function:

function get(&$var, $default = null)
{
  return isset($var) ? $var : $default;
}

Use it like that:

$sent = get($_POST['chat'], '');

or just

$sent = get($_POST['chat']);

edited Apr 30, 2016 at 5:48

answered Apr 30, 2016 at 5:42

Pinke Helga

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