$re = '/((?:0|[1-9]\d*)?(?:\.\d+)?)\s*\b(rld[\W_]*token|btcc|btc|ark|xmr|xrp)\b/m';
$str = 'price of rldtoken
420 rld.token 0.28 btc
42.37 rldtoken to xrp
42.37rldtoken to xmr
cost of rldtoken
10 btc 12.47 rldtoken to xmr
whatisrldtoken
btcc price
btc cost
0.2btc';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php