I have got the following phrase:
Mark: 5 Mike 2015-01-20
Mark:<optional spaces><digits><optional spaces> is a prefix
for the search string (our "Mike"), and the search string is a sequence of non-space
characters, then the following should do:
preg_match('/Mark\:\s*\d+\s*(\S+)/', $the_string, $m); // $m = 'Mike'
If the search string is supposed to be something more complex, then just replace
with the desired pattern. You haven't specified this case, so I can't help