$re = '/JSESSIONID=([^;]*)/';
$str = 'Set-Cookie:Apache=40.76.87.14.1462996905538733; path=/; domain=.cra-arc.gc.ca,JSESSIONID=KjahaS5VdMBttn9bAYuS_iHFXOgmqQyMxHcht1kBS7p1YOpdV2V_!1094217526; path=/; HttpOnly';
preg_match($re, $str, $matches, PREG_OFFSET_CAPTURE, 0);
// Print the entire match result
var_dump($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