I have next code:
<?
$testline = "a"."\1"."b"."\0"."d"."\1"."f"."\1"."1"."\1"."d";
var_dump(explode("\1",$testline));
?>

In PHP 4.2.3 it work as expected, I see:
array(5) { [0]=> string(1) "a" [1]=> string(3) "bd" [2]=> string(1) "f" [3]=> string(1) "1" [4]=> string(1) "d" } 

In PHP 4.3pre1:
array(2) { [0]=> string(1) "a" [1]=> string(9) "bd
f
1
d" } 

Same effect if "\0" replace to "\2".

My config line:
'./configure' '--with-apxs=/usr/local/apache/bin/apxs' '--with-pfpro' '--enable-inline-optimization' '--with-mysql' '--enable-track-vars' '--disable-debug' '--disable-pic' '--disable-ctype' '--disable-mbstring' '--disable-xml' '--disable-tokenizer' '--with-zlib' '--enable-sysvshm' '--enable-sysvsem' '--enable-shmop' '--enable-costaid' '--with-mm' '--with-imap=/usr/install/imap-2002.RC5' '--with-gdbm' '--with-oci8' '--enable-sigchild' '--without-gd' '--with-curl' '--with-dom-exslt' '--with-dom-xslt' '--with-dom'