You can use the strpos function which is used to find the occurrence of one string inside other:
if (strpos($a,'are') !== false) {
echo 'true';
}
Note that the use of !== false is deliberate; strpos
returns either the offset at which the needle string begins in the haystack string, or the boolean false
if the needle isn't found. Since 0 is a valid offset and 0 is "falsey", we can't use simpler constructs like !strpos($a, 'are').