Description:
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This code read a file(bcgm.txt) and use regex to process the content,then write a new file(yes.txt)! I try it on PHP5.1.6,the result is just fine,but If I run it on PHP2.X the result file is bad and just a NULL in the file.
    And Then ,I try other method ,Let the content short ,it's also OK,but let the content keep very long,the problem is still.
    

    preg_match_all() cannot matches very long string.

Reproduce code:
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http://forideal.blog.163.com/blog/

Expected result:
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one new file,which contains the result string.

Actual result:
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But in the file just is "null".