$re = '/^([\w-]+[\W\r\n]+[\w-]+).+/m';
$str = 'AO SMITH 100108283 4500W/240V SCREW-IN ELEMENT, 11
BRA14X18HEBU / P11-042 / 310-470NL BRASS 1/4 x 1/8 HEX BUSHING
TWO-HOLE PIPE STRAP 4" 008004EG 72E 4';
$subst = "$1";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
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