php stristr
#Case-insensitive strstr()
#stristr(string $haystack, string $needle, bool $before_needle = false): string|false
#Returns all of haystack starting from and including the first occurrence of needle to the end.
<?php
$email = '[email protected]';
echo stristr($email, 'e'); // outputs [email protected]
echo stristr($email, 'e', true); // outputs US
?>