PHP regular expression to filter spaces, newlines, and carriage returns_PHP Tutorial

$str = " This line　 containstliberal rn use of　　 whitespace.nn"; 
// First remove the leading/trailing whitespace 
//去掉开始和结束的空白  www.111cn.net
$str = trim($str); 
// Now remove any doubled-up whitespace 
//去掉跟随别的挤在一块的空白 
$str = preg_replace('/s(?=s)/', '', $str); 
// Finally, replace any non-space whitespace, with a space 
//最后，去掉非space 的空白，用一个空格代替 
$str = preg_replace('/[nrt]/', ' ', $str); 
// Echo out: 'This line contains liberal use of whitespace.' 
echo "

{$str}

{$str}

//1、使用str_replace 来替换换行 
$str = str_replace(array("rn", "r", "n"), "", $str);

//2、使用正则替换 
$str = preg_replace('//s*/', '', $str);

//3、使用php定义好的变量 （建议使用） 
$str = str_replace(PHP_EOL, '', $str);

//php line breaks in different systems
//The implementation of line breaks is different between different systems
//Used in linux and unix /n
//For MAC /r
//window In order to reflect the difference from linux, it is /r/n
//So the implementation methods are different on different platforms
//php has three ways to solve it
                                                                                //1. Use str_replace to replace newlines
$str = str_replace(array("/r/n", "/r", "/n"), "", $str);
                                                                                //2. Use regular replacement
$str = preg_replace('//s*/', '', $str);
                                                                                //3. Use variables defined by php (recommended)
$str = str_replace(PHP_EOL, '', $str);
?>