$re = '/IllegalArgumentException\n\s*at\s+(.+)(?:\n\s*at(?!\s*com\.test).*)*\n\s*at\s+((com\.test[^(\n]*).*)(?:\n\s*at.*)*\n\s*at\s+(?!\3)(com\.test.*)/m';
$str = 'IllegalArgumentException
at org.eclipse.jface.action.ActionContributionItem.handleWidgetSelection(ActionContributionItem.java:584)
at java.security.AccessController.doPrivileged(Native Method)
at org.eclipse.ui.internal.Workbench.runEventLoop(Workbench.java:2640)
at org.eclipse.ui.internal.Workbench.runUI(Workbench.java:2604)
at com.test.package1.user1.client1.client1.Call.invoke(Call.java:90)
at org.eclipse.ui.internal.Workbench.access$4(Workbench.java:2438)
at org.eclipse.ui.internal.Workbench$7.run(Workbench.java:671)
at com.test.package1.user1.client1.client1.Call.invoke(SrvCall.java:84)
at org.eclipse.ui.internal.Workbench.runEventLoop(Workbench.java:2640)
at java.security.AccessController.doPrivileged(Native Method)
at com.test.package2.user2.client2.client2.Call.invoke(Call.java:90)
at org.eclipse.ui.internal.Workbench.runEventLoop(Workbench.java:2640)
at org.eclipse.ui.internal.Workbench.runUI(Workbench.java:2604)
at org.eclipse.ui.internal.Workbench.access$4(Workbench.java:2438)
at org.eclipse.ui.internal.Workbench$7.run(Workbench.java:671)
';
preg_match_all($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