检查值是否存在大写和小写字母

Question

I want to check if username exists in Database but I have problem Ex : If I have username = jack and another register with username = JaCk

It accepts I want to check the full username with lowercase and uppercase and refuse such cases (jack - Jack - JaCk ....)

$stmtr = $DB_con->prepare("SELECT username FROM users WHERE username=:username");
$stmtr->bindparam(":username", $val['username']);
$stmtr->execute();
$row=$stmtr->fetch(PDO::FETCH_ASSOC);

if($rowr['username']==$val['username']) {
echo "Exists";
}

Answer 1

There is a typo. In line:

if($rowr['username']==$val['username']) {

it should be:

if($row['username']==$val['username']) {

Also, by default, MySQL performs case-insensitive query. Note the _ci part in your DB collation (eg utf8_general_ci ), it means case insensitive. You have to perform extra checking in PHP to check for different upper- and lowercase.

Answer 2

 if( strtolower($row['username'])==strtolower($val['username']) ) { echo "Exists";}

You can also replace strtolower with strtoupper that will convert a string to upper case.

NOTE: That for this case strtolower and strtoupper will result in the same outcome as noted by @user3783243

Also if your trying to compare both values with Case Sensitivity that is you don't want if('JAck'== 'jAck') to return true then use strict comparison ===

 if('JAck'== 'jAck') //will return true
 if('JAck'=== 'jAck') //will retrun false

Answer 3

You can using UPPER_CASE in SQL query:

$stmtr = $DB_con->prepare("SELECT username FROM users WHERE UPPER(username)=:username");
$stmtr->bindparam(":username", strtoupper($val['username']));

But I think you should store username as uppercase or lowercase when user register. It is better than using UPPER in SQL