$re = '/\s?(\w+)(?=:)/m';
$str = 'Martin: Let\'s show Mr. Hooper our, uh, hex. Here. " +
"Hooper: Ah, victim identified as Christine Watkins. Female Caucasian. " +
"Martin: Yeah now, now here\'s where we have it. " +
"Hooper: Probable boating accident. Martin: Yeah. " +
"Hooper: The height and weight of the victim can only be estimated from the partial remains. The torso has been severed in mid-thorax. There are no major organs remain.';
preg_match_all($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