PHP Notice: Array to string conversion Error - php

Question

Been experiencing this error for a little while and can't find any conclusive answers on fixing it. I have tried removing quotes from $key in line 59 but to no avail.
if (!get_magic_quotes_gpc()) {
if (isset($_POST)) {
foreach ($_POST as $key => $value) {
$_POST['$key'] = trim(addslashes($value));
}
}
if (isset($_GET)) {
foreach ($_GET as $key => $value) {
$_GET[$key] = trim(addslashes($value));
}
}
}
LINE 59
$_POST['$key'] = trim(addslashes($value));
Error On Screen
Notice: Array to string conversion in
C:\Inetpub\vhosts\domain.com\httpdocs\library\config.php on
line 59

Answer 1

Check if it is array before you assign it
$_POST[$key] = !is_array($value) ? trim(addslashes($value)) : '';
// ^ Remove the quotes here // ^ Do something
// Instead of
// Using empty

Answer 2

According to PHP.net the function addslashes() takes a String type as parameter. Check what type $value is. If it is an array itself then addslashes() may be throwing the error.
PS:
You should use $_POST[$key] rather than $_POST['$key'] if you want to use the value of $key as the index of the $_POST array.

Answer 3

I think you should use this code $_POST[$key] = $value; instead of using this $_POST['$key'] = trim(addslashes($value));
or make a check if the value is in array or not

Answer 4

Do this:
foreach ($_POST as &$value) {
$value = is_array($value) ?
array_map(function($x) { return trim(addslashes($x)); } :
trim(addslashes($value));
}
However, this could still fail if any of your parameters are multi-dimensional arrays. As mentioned in the comments, the right solution is to use prepared queries with parameters, rather than interpolating strings into SQL.