如何从右边向左截取字符串

回复讨论(解决方案)

substr可以用负数，详情参考：
http://cn2.php.com/manual/zh/function.substr.php

可以使用"_"作为分割符，数组操作。

[code=php][ $str='001_002_003';
$find='_003';
echo substr($str,0,strpos($str,$find))
?>/code]

$s = '001_002_003';echo substr($s, 0, -4);//001_002echo substr($s, 0, strrpos($s, '_'));//001_002echo join('_', array_slice(explode('_', $s), 0, -1));//001_002echo strrev(substr(strrev($s), 4));//001_002

$str = '001_002_003';$data = explode('_',$str);krsort($data);foreach($data as $row)echo $row.'
';

$str = '001_002_003_004_005_006_007';$data = explode('_',$str);krsort($data);$total = count($data);$need = $total - 3;foreach($data as $k=>$row){	if($k<$need){		echo $row.'
';	}}

没看清题目，6楼的不算，7楼的应该是LZ要求的条件吧？

参考：

substr可以用负数是正解