Description:
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It seems that bug #29865 is back: in release 5.2.5 serialize() uses "ASCII 0" to serialize private property names.

Reproduce code:
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% php -r 'class A { private $t;} echo serialize(new A());'|hexdump -C

Expected result:
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00000000  4f 3a 31 3a 22 41 22 3a  31 3a 7b 73 3a 34 3a 22  |O:1:"A":1:{s:4:"|
00000010  ** 41 ** 74 22 3b 4e 3b  7d                       |.A.t";N;}|

Actual result:
--------------
00000000  4f 3a 31 3a 22 41 22 3a  31 3a 7b 73 3a 34 3a 22  |O:1:"A":1:{s:4:"|
00000010  00 41 00 74 22 3b 4e 3b  7d                       |.A.t";N;}|