$re = '/(Source_addresses:(?:.|\n)*?Applications:.*\n)/';
$str = 'Policy name: example-3 (lf-csd) (LINE 29907)
Description: CHANGE00001
Destination_addresses (8):
10.0.0.1/32 ( 10.0.0.1-lk-3r53) ( 3125)
10.0.0.8/32 ( 10.0.0.8-test13) ( 3157)
10.0.0.3/32 ( 10.0.0.3-gdgsd-cd) ( 2806)
10.0.0.9/32 ( 10.0.0.9-fd-fdsb) ( 3123)
Destination_address_sets (0):
Source_addresses:
10.0.0.7/32 ( 10.0.0.7-IR) ( 5989)
Applications: tcp3389
Then: permit
Policy name: example-4 (lfs-csd) (LINE 29907)
Description: CHANGE00002
Destination_addresses (3):
10.0.0.6/32 ( 10.0.0.1-lk-3r53) ( 3125)
10.0.0.2/32 ( 10.0.0.8-test13) ( 3157)
10.0.0.53/32 ( 10.0.0.3-gdgsd-cd) ( 2806)
10.0.0.94/32 ( 10.0.0.9-fd-fdsb) ( 3123)
Destination_address_sets (0):
Source_addresses:
10.0.0.53/32 ( 10.0.0.52-IR) ( 5989)
Applications: tcp53
Then: permit';
preg_match_all($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