How to split a string in PHP

I have a long string resulted from en开发者_开发知识库coding a binary file -an image file- (in base 64). Is there a particulary method (or rule) I should follow when spliting it?

Edit:

I want to write the string to a xml file, but in order to do this I must split it in smaller chunks.

Edit2:

I would like to split it by length (I think that is more appropriate in this case).

Thank you.

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You might want to take a look at chunk_split(), since you do base64 encoding. (Assuming you do encoding, since you can't embed decoded base64 data in XML files)

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Use explode() or preg_split() as appropriate. All data in PHP is technically binary, even character data. If your data is multibyte character data (eg UTF-8) you'll need extra steps to correctly handle that.

Also binary strings may need processing with unpack().

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chunk_split (string $body [, int $chunklen [, string $end ]] )