Description:
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From manual page: http://www.php.net/function.strpos
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hope add $endpos to the function strpos, like: strpos($str,$find,$startpos,$endpos).

then we can efficient to get the result when we need to find pos in a long string, even in a file...

otherwise we need to use substr() additional...

希望在strpos函数中增加一个截止位置参数，像strpos($str,$find,$startpos,$endpos)，否则相关需求会调用substr()增加开销

Test script:
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$str="www123xxxxxxxxxxxxxxxxxxxxxxx789yyyyyyyyyyyyyyyyyyy456yyyyyyyyyyyyyyyyy";
$n=strpos($str,'456',5,20);


Expected result:
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$n==false, or $n==-1