How to separate a long string to short string with space each 5 character in php?

[nhbach]

I have a long string in db

$code = "ACTGTCTACTGGTC TAGCTAGTCATGCTA GTAATCG"
How to separate a long string to short string with space each 5 character?
Example:

ACTGT CTACT GGTCT AGCTA GTCAT GCTAG TAATC
Please help me, i am a biology student! Thanks!

[Dormilich]

try chunk_split(). I was a Chemistry student.

[nhbach]

Thank you in advanced.
And, if i want to numbered the character in string when I use wordwap to break line this string, what I can do?

Example:
$str1 = "GCCGGCGGCCAGGG CGAGCGCTTGCTGGC "
$str2 = "GCCGG CGGCC AGGGC GAGCC TTGCT GGC" (i can do that now, thanks)

And:
1 GCCGG CGGCC
11 AGGGC GAGCC
21 TTGCT GGC

Please help me! Thanks