- preg_match: documentation ( source)
<?php
print preg_match('/^[a-z0-9 _.*",?{}@!=:;\/+~\\-]+$/i', 'v=DKIM1; k=rsa; p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDLVTHyanj4Pvh8Ye3vcOpvG29URNNbESNvjgfx8F12rig2Pd5gp1Y6NAZQgWzEFpDjeAMnFdpS+5U5XIAXz7nWVA061DXTXE2cvzHXGA0W8sLDOvdk3K7PXCRs1/c6JUgIhE+ViZebpShS3x4W72ooUXS2KvWe/ArpiF0Q+qrUlwIDAQAB');