php - Replace in one step based on matched result -

i have string , want each yyyy-mm-dd hh:mm:ss date time string replaced unix timestamp.

i have managed far identifying date time strings occur:

$my_string = 'hello world 2014-12-25 10:00:00 , foo 2014-09-10 05:00:00, bar';  preg_match_all('((?:2|1)\\d{3}(?:-|\\/)(?:(?:0[1-9])|(?:1[0-2]))(?:-|\\/)(?:(?:0[1-9])|(?:[1-2][0-9])|(?:3[0-1]))(?:t|\\s)(?:(?:[0-1][0-9])|(?:2[0-3])):(?:[0-5][0-9]):(?:[0-5][0-9]))',$my_string,$my_matches, preg_offset_capture);  print_r($my_matches); 

this outputs array of arrays containing value of date time string matched , location:

array (     [0] => array         (             [0] => array                 (                     [0] => 2014-12-25 10:00:00                     [1] => 12                 )              [1] => array                 (                     [0] => 2014-09-10 05:00:00                     [1] => 40                 )          )  ) 

from point going loop through arrays , replace based on str_replace() , strtotime() i'm thinking have lower execution time if this:

$my_string = preg_replace(     '((?:2|1)\\d{3}(?:-|\\/)(?:(?:0[1-9])|(?:1[0-2]))(?:-|\\/)(?:(?:0[1-9])|(?:[1-2][0-9])|(?:3[0-1]))(?:t|\\s)(?:(?:[0-1][0-9])|(?:2[0-3])):(?:[0-5][0-9]):(?:[0-5][0-9]))',     strtotime($value_of_matched_string),     $my_string ); 

so every found instance of matched made strtotime() format.

what correct way result? looping feasible way?

use preg_replace_callback() instead. allows perform search , replace using callback function:

echo preg_replace_callback($pattern, function ($m) {     return strtotime($m[0]); }, $my_string); 

$m array containing matched items. $m[0] contains date string.

the above code output:

hello world 1419501600 , foo 1410325200, bar 

demo