$str = 'abcdef';echo strrev($str);

$str = '字符串反轉(zhuǎn)';function rev($str, $encoding = 'utf-8'){ $len = mb_strlen($str); $result = ''; for ($i = $len-1; $i>=0; $i--){  $result.= mb_substr($str,$i,1,$encoding); } return $result;}echo rev($str);

$str = 'abcdefg';$len = strlen($str);$times = $len/2;for($i = 0;$i <= $times; $i++ ){ $tmp = $str[$i]; $str[$i] = $str[$len-$i-1]; $str[$len-$i-1] = $tmp;}echo $str;