PHP Unique random string generator - php

Question

How to make a random string unique to the string in the column below?
<?php
$n=10;
function getName($n) {
$characters = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
$randomString = '';
for ($i = 0; $i < $n; $i++) {
$index = rand(0, strlen($characters) - 1);
$randomString .= $characters[$index];
}
return $randomString;
}
echo getName($n);
?>

Answer 1

<?php
$n = 10;
function getName($n) {
$characters = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
$randomString = '';
for ($i = 0; $i < $n; $i++) {
$index = rand(0, strlen($characters) - 1);
$randomString .= $characters[$index];
}
return $randomString;
}
function getUniqueString($length, $dbConnection){
$string = getName($length);
$count = $dbConnection->query("SELECT * FROM TABLE_NAME WHERE string='$string')")->num_rows;
while($count != 0){
$string = getName($length);
$count = $dbConnection->query("SELECT * FROM TABLE_NAME WHERE string='$string')")->num_rows;
}
return $string;
}
echo getUniqueString($n, $dbConnection);
?>

Answer 2

You can use openssl_random_pseudo_bytes() or random_bytes() PHP fonction to generate random strings.
You can also rely on MySQL to generate uniq IDs :
INSERT INTO mytable (alphaID) VALUES (REPLACE( UUID(), '-', '' ));