Wordpress: PHP delete database row in foreach cycle - php

Question

Hi guys I am very new to PHP development.
I am writing a smiple script to get and email perameter from the url, cycle through some rows in a database table and delete the row if it is found.
I have got everything except the deleting of the row. I would really appreciate someone talking me through my mistake to help me understand. I think the error lies in the WHERE condition.
The error message I get is:
ERROR: Could not able to execute DELETE FROM wp_email_address_db WHERE alaofolasade#yahoo.com==alaofolasade#yahoo.com.
<?php
$path = $_SERVER['DOCUMENT_ROOT'];
include_once $path . '/wp-load.php';
global $wpdb;
//sanatise and lowercase email addy from URL
$emailToRemove = filter_var ( strtolower($_GET["usermail"]), FILTER_SANITIZE_EMAIL);
//get DB table
$data = $wpdb->get_results("SELECT * FROM wp_email_address_db`");
foreach ($data as $d) {
//sanatise and lowercase email addy from DB
$email = filter_var ( strtolower($d->email_address), FILTER_SANITIZE_EMAIL);
//check if the email addy is in this row
if($email == $emailToRemove){
//get info
echo 'true <br/>';
echo 'id: '.$d->id.'<br/>';
//I need to delete this row
$sql = "DELETE FROM wp_email_address_db WHERE $email = $emailToRemove";
if(mysqli_query($link, $sql)){
echo "Records were deleted successfully.";
} else{
echo "ERROR: Could not able to execute $sql. " . mysqli_error($link);
}
}
}
// $columnTitles = ['id','email_address','imported_via'];
?>

Answer 1

You have a typo in email and the value in where clause should be within single quotes:
change this to:
$sql = "DELETE FROM wp_email_address_db WHERE email = '$emailToRemove'";

Answer 2

Your query should be this :
$sql = "DELETE FROM wp_email_address_db WHERE email = '$emailToRemove'";

Answer 3

It is always better to use quotation (single quote', double quote ") also defining the column with back-tick.
Query:
$sql = "DELETE FROM wp_email_address_db WHERE `email` = '".$emailToRemove."'";
Your main error is $email which should be the column name with back-tick here WHERE $email = $emailToRemove

Answer 4

Should not be the query something like
DELETE FROM wp_email_address_db WHERE email_field_name = '$emailToRemove'
instead of
DELETE FROM wp_email_address_db WHERE $email = $emailToRemove
In your query you are passing the value of $email as field name and I assume that the field alaofolasade#yahoo.com does not exist

Answer 5

Try replacing
$sql = "DELETE FROM wp_email_address_db WHERE $email = $emailToRemove";
with
$sql = "DELETE FROM wp_email_address_db WHERE '$email' = '$emailToRemove'";

Answer 6

I removed the foreach, you don't need to retrieve ALL the mails from your database.
Moreover I used the prepared statements to avoid SQL injections
This kind of script which perform delete query to database HAVE to be protected from all users. Only admins should be allow to this script
<?php
$path = $_SERVER['DOCUMENT_ROOT'];
include_once $path . '/wp-load.php';
// WARNING: You should check the identity of the user performing this action, MySql DELETE action is dangerous
global $wpdb;
//sanatise and lowercase email addy from URL
$emailToRemove = filter_var ( strtolower($_GET["usermail"]), FILTER_SANITIZE_EMAIL);
$sqlDeleteQuery = '
DELETE
FROM wp_email_address_db
WHERE email = ?
';
$statement = mysqli_prepare($link, $sqlDeleteQuery);
// Bind the email to your query (the ? ), this avoid the SQL injection attack
$statement->bind_param('s', $emailToRemove);
if (false !== mysqli_stmt_execute($statement)) {
die('The MySql query failed ! Error : ' . mysqli_error($link));
}
$emailsDeleted = mysqli_stmt_affected_rows($statement);
echo sprintf('"%d" emails deleted', $emailsDeleted);
I can't try the above code, so please let me know if something is wrong :)

Answer 7

Solved it by:
<?php
require_once($_SERVER["DOCUMENT_ROOT"]."/wp-load.php");
if (isset($_GET["usermail"])) {
global $wpdb;
$remove = filter_var(strtolower($_GET["usermail"]), FILTER_SANITIZE_EMAIL);
$wpdb->query("DELETE FROM wp_email_address_db WHERE email_address='$remove'");
echo "You have successfully been unsubscribed.";
}
?>