test.php

<?php

function pickupFromTextArea($needle, $subject) {
  $pattern = "/{$needle}(.*)/";
  if (preg_match($pattern, $subject, $matches) === 1) {
    return trim($matches[1], "\r");
  }
  return false;
}

$textarea  = "発着地を入力下さい。
出発地：上野
到着地：大井町
";


var_dump(pickupFromTextArea("出発地：", $textarea));
var_dump(pickupFromTextArea("到着地：", $textarea));