Question

ANSWER EDIT:

The fix was to change:

if (get_user_data( $input_user, $logindata ) === $input_pwd ) {

to
if (get_user_data(strtolower($input_user), $logindata) === $input_pwd ) {

so that the username is forced to lowercase. I just have to be conscious to store my usernames as all lowercase too.

I am aware of strcasecmp. I am not sure how that would apply to my working code though, as you can only compare 2 variables.

Am I able to make preg_match case insensitive in the context of my working code below?
Can I add the /i regex to my preg_match command to a returned variable?

I just want the username that is entered by the user (including domain name) to be case insenstive. (ie. [e-mail]) without having to add every combination of valid username to my pseudo database!

This is my working code:

// Get users
$input_pwd = ( isset( $_POST["password"] ) ? $_POST["password"] : '' );
$input_user = ( isset( $_POST["username"] ) ? $_POST["username"] : '' );

// Your pseudo database here
$usernames = array(
"[e-mail]",
"[e-mail]",
"[e-mail]",
"[e-mail]", 
"/[a-z][A-Z][0-9]@domain2\.com/",   // use an emtpy password string for each of these
"/[^@]+@domain3\.com/"              // entries if they don't need to authenticate
);

$passwords = array( "password1", "password2", "password3", "password4", "", "" );

// Create an array of username literals or patterns and corresponding redirection targets
$targets = array(
"[e-mail]"           => "http://www.google.com",
"[e-mail]"          => "http://www.yahoo.com",
"[e-mail]"          => "http://www.stackoverflow.com",
"[e-mail]"          => "http://www.serverfault.com",
"/[a-z][A-Z][0-9]@domain2\.com/" => "http://target-for-aA1-usertypes.com",
"/[^@]+@domain3\.com/"           => "http://target-for-all-domain3-users.com",
"/.+/"                           => "http://default-target-if-all-else-fails.com",
);

$logindata = array_combine( $usernames, $passwords );

if ( get_user_data( $input_user, $logindata ) === $input_pwd ) {

   session_start();
   $_SESSION["username"] = $input_user;
   header('Location: ' . get_user_data( $input_user, $targets ) );
   exit;

} else {
// Supplied username is invalid, or the corresponding password doesn't match
   header('Location: login.php?login_error=1'); 
   exit; 
}

function get_user_data ( $user, array $data ) {

    $retrieved = null;

    foreach ( $data as $user_pattern => $value ) {

        if (
               ( $user_pattern[0] == '/' and preg_match( $user_pattern, $user ) )
            or ( $user_pattern[0] != '/' and $user_pattern === $user)
        ) {
            $retrieved = $value;
            break;
        }
    }
    return $retrieved;
}

Answer 1

You can do a case insensitive match in PHP with i. For instance, the following will print ‘This matches!’:

<?php
if ( preg_match('/def/i', 'ABCDEF') ) {
    echo 'This matches!';
}
?>

So just add i to the pattern, and the case will be ignored.