$re = '/uniprotkb:(.*?)[-(][a-zA-Z]/m';
$str = 'uniprotkb:P62158(protein(MI:0326), 9606 - Homo sapiens)
uniprotkb:O00602-PRO_0000009136(protein(MI:0326), 9606 - Homo sapiens)';
preg_match_all($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