Description:
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I'm test set_time_limit function with no param,it trow an warning info.I have see description in online manual:
When called, set_time_limit() restarts the timeout counter from zero. In other words, if the timeout is the default 30 seconds, and 25 seconds into script execution a call such as set_time_limit(20) is made, the script will run for a total of 45 seconds before timing out. 

It's means this function with no param must work well.

BTW:I'm test codes in php6-dev and php 5.2.9 all of them trow an warning.:(

Reproduce code:
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set_time_limit(50);
set_time_limit();
exit;

Expected result:
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Warning: set_time_limit() expects exactly 1 parameter, 0 given in xxxxxxx on line 3
PHP Warning: set_time_limit() expects exactly 1 parameter, 0 given in xxxxxxx on line 3