Bob Gilder birdied the eighth hole of a sudden-death playoff and won first prize of $63,000 in the Phoenix Open golf tournament today as, for the second week in a row, Rex Caldwell became an extra-hole loser.

Caldwell, a playoff victim last week in the Bob Hope Desert Classic, made a four-man field for sudden death here when he dropped a 30-foot birdie putt on the last hole of regulation play.

Mark O'Meara and Johnny Miller also finished regulation at 271, 13 shots under par on the rain-soaked Phoenix Country Club course, but they were eliminated on the second extra hole. Caldwell and Gilder battled on until Gilder ended it with a seven-foot birdie putt in the lengthening shadows of late afternoon. Calder's 17-footer had lipped the hole.

Caldwell, still seeking his first title in nine years on the PGA Tour, played the last round in 70. O'Meara had 66, Miller 68 and Gilder 69. Caldwell, O'Meara and Miller each won $26,133, deemed tied for second.

Starting the playoff on the 15th hole, all four shot par. Caldwell and Gilder birdied 16.

The survivors parred the 17th and 18th, returned to 15 and parred along until they returned to 18. Caldwell had made the playoff with a birdie on the 18th, hitting his third shot out of the trees and holing a putt from about 30 feet, but this time he found no magic.

At one time or another over the last nine holes of regulation, seven players led or shared the lead. Ed Sneed, Tim Simpson, Hal Sutton, Cal Peete and Scott Hoch ended at 272.

Gilder said he got a break when his second shot on the winning hole hit and stopped short of the green.

"The worst thing that could have happened would have been if it had trickled onto the front of the green," he said. "I'd been having trouble all day with long putts. As it was, I got to chip up close with a six-iron."

Caldwell, who lost to Keith Fergus on the first extra hole last week, left the course here without commment.