1.單字節字符串反轉

php提供了現成的用於字符串反轉的函數strrev()

$str = ‘abcdef123‘;
echo strrev($str)

2.對於包含中文的多字節字符串需要用到mb_substr()

$str = ‘字符串反轉‘;

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);

3.算法實現 首位交換

$str = ‘abcdefg123‘;
$len = strlen($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;

字符串反轉方法收集