$re = '/\|Transition Reason:(?<Transiction_Reason>[^\|]*)\|/m';
$str = 'Data1: |Transitioned to:Team1|Transition Reason:Out of Scope|handledbySomeone3|
Data2: |Transitioned to:Team2|Transition Reason:Invalid Description|handledbySomeone2|
Data3: |Transitioned to:Team3|Transition Reason:Incomplete Details|handledbySomeone1|';
preg_match_all($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