mysqli_query() always return true

Question

This is my form:

<!DOCTYPE html>
<html>
  <head>
  </head>
  <body>
    <form action="register_ajax.php" method="get">
    <input type="text" name="email">
    <input type="submit" value="test">
    </form>
  </body>
</html>

This is my php code:

<?php
    $dbc = mysqli_connect("localhost","root","*******","continental_tourism") OR die(mysqli_connect_error());
    $email = $_GET['email'];
    $query = "SELECT email FROM customer_info WHERE email = '$email' ";
    $r = mysqli_query($dbc, $query) OR die(mysqli_error($dbc));
    if($r)
        echo "Email address exists!";
    else
        echo "sss";
?>

If I enter a correct(Existing email on db) $r is true. But if I enter non existing email, then also $r is true. Why is that? Basically I want to detect the empty set. How can I do it?

Thanks!

first of all, use mysqli_real_escape_string() on $_GET['email'] — hjpotter92, Apr 17 '12 at 15:46
what you are doing is wrong, you checking if the database is querying which is always gonna be true in your case...what you need to do is check the number for rows returning from the query — dansasu11, Apr 17 '12 at 15:48

score 14 · Accepted Answer · edited Sep 22 '21 at 09:22

14

$r will only be false if there was SQL error. Otherwise it will always return an object, even if no rows are returned by your SELECT statement.

Use mysqli_num_rows() to count how many rows are returned. Zero means no one is using that email address.

if(mysqli_num_rows($r))
    echo "Email address exists!";
else
    echo "sss";

edited Sep 22 '21 at 09:22

Dharman

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answered Apr 17 '12 at 15:45

John Conde

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DaveRandom · Answer 2 · 2012-04-17T15:54:45.507

mysqli_query() will always returns a MySQLi result resource if the query was successful. A resource will always evaluate to TRUE when tested as a boolean.

A successful query is not necessarily one that returns results, it is simply a query that did not fail. Queries are considered to have failed when there is an error, for example a syntax error or a processing error within the MySQL server - which case they will return FALSE. But a query that finds no results is still a successful query.

You need to use mysqli_num_rows() to determine whether the query found any results:

<?php
    $dbc = mysqli_connect("localhost","root","longhorn","continental_tourism") OR die(mysqli_connect_error());

    $email = $_GET['email'];

    $query = "SELECT email FROM customer_info WHERE email = '$email' ";

    $r = mysqli_query($dbc, $query) OR die(mysqli_error($dbc));

    if(mysqli_num_rows($r) > 0)
        echo "Email address exists!";
    else
        echo "sss"; 
?>

Alex Turpin · Answer 3 · 2013-09-30T16:44:08.417

0

mysqli_query will return a result object on success and false on failure. No rows selected is not considered failure. You can use mysqli_num_rows to check the number of rows returned.

edited Sep 30 '13 at 16:44

answered Apr 17 '12 at 15:48

Alex Turpin

46,743
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score 0 · Answer 4 · edited Aug 08 '18 at 11:29

0

One needs to test to see if $r is true, and if row count is greater than 0.

The following works:

if ($r and mysqli_num_rows($r) > 0) {

  echo "rows exist"; } else {

echo "rows don't exist";  }

edited Aug 08 '18 at 11:29

Yannis

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answered Aug 08 '18 at 10:47

Irfan Virk

1

mysqli_query() always return true

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