去除字符串内部的空行：
$str = preg_replace("/(\s*?\r?\n\s*?)+/","\n",$str);
去除全部的空行，包括内部和头尾：
$str = preg_replace('/($\s*$)|(^\s*^)/m', '',$str);
editplus中替换空白行的正则表达式：
正则表达式：^[\t\n ]*\n
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