Using regex to extract first half of string

Question

I have variable strings like the below:
The.Test.String.A01Y18.123h.WIB-DI.DO5.1.K.314-ECO
The.Regex.F05P78.123h.WIB-DI.DO5.1.K.314-EYT
Word.C05F78.342T.DSW-RF.EF5.2.F.342-DDF

I would like to extract this part of these string in PHP dynamically and i was looking at using regex but haven't had much success:
The.Test.String.A01Y18
The.Regex.F05P78
Word.C05F78

And ultimately to:
The Test String A01Y18
The Regex F05P78
Word C05F78

The first part of the text will be variable in length and will separate each word with a period. The next part will always be the same length with the pattern:
One letter, 2 number, one letter, 2 numbers pattern (C05F78)

Any thing in the string after that is what I would like to remove.

Answer 1

that's it

$x=array(
    "The.Test.String.A01Y18.123h.WIB-DI.DO5.1.K.314-ECO",
    "The.Regex.F05P78.123h.WIB-DI.DO5.1.K.314-EYT",
    "Word.C05F78.342T.DSW-RF.EF5.2.F.342-DDF"
);

for ($i=0, $tmp_count=count($x); $i<$tmp_count; ++$i) {
    echo str_replace(".", " ", preg_replace("/^(.+?)([a-z]{1}[0-9]{2}[a-z]{1}[0-9]{2})\..+$/i", "\\1\\2", $x[$i]))."<br />";
}

Answer 2

Using this regular expression should work, replacing each of your strings with the first capturing group:

^((?:\w+\.)+\w\d{2}\w\d{2}).*

See demo at http://regex101.com/r/fR3pM6

Answer 3

This is valid too:

preg_match("\.*[\w\d]{6}", stringVariable)

.* for all digits atleast we found a composition of letters and words of 6 characters ([\w\d]{6})

Result:

Match 1:    The.Test.Stsrisng.A01Y18    
Match 2:    The.Regex.F05P78       
Match 3:    Word.C05F78