字符串函数
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strrev

(PHP 4, PHP 5)

strrev — 反转字符串

说明

string strrev ( string $string )

返回 string 反转后的字符串。

参数

string

待反转的原始字符串。

返回值

返回反转后的字符串。

范例

Example #1 使用 strrev() 反转字符串

<?php
echo strrev("Hello world!"); // 输出 "!dlrow olleH"
?>

字符串函数
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PHP手册 - N: 反转字符串

用户评论:

dyaskur at gmail dot com (28-Mar-2012 07:09)

This is funny function for write upside down:
<?php

function strflip($text)
{
  $text=strrev($text);
  $text=strtolower($text);

$arr = array(
"a" => "&#x250;",
"b" => "q",
"c" => "&#x254;",
"d" => "p",
"e" => "&#x01DD;",
"f" => "&#x25F;",
"g" => "&#x387;",
"h" => "&#x0265;",
"i" => "&#x0131;",
"j" => "&#x027E;",
"k" => "&#x029E;",
"l" => "&#x0283;",
"m" => "&#x026F;",
"n" => "u",
"p" => "d",
"q" => "b",
"r" => "&#x0279;",
"t" => "&#x0287;",
"u" => "n",
"v" => "&#x028C;",
"w" => "&#x028D;",
"y" => "&#x028E;",
"B" => "D"
);
$result = strtr($text,$arr);
return $result;
}
$text = "My name is Dyas Yaskur";
echo strflip($text); //?n?s?? s??p s? ???u ??
?>

qeremy [atta] gmail [dotta] com (25-Feb-2012 12:34)

An easy way for unicode string reversing;

<?php
function strrev_utf8($str) {
    return join("", array_reverse(
        preg_split("//u", $str)
    ));
}

$str = "?eker y?rim!"; // My sugar love
echo $str."\n";
echo strrev($str)."\n"; // !mir??y reke??
echo strrev_utf8($str); // !mir?y reke?
?>

lwc at trashymail dot com (19-Jun-2008 01:00)

manfred at werkzeugH dot at, your version works, but do you think it has an advantage over mine? Just wondering if I should update my scripts.

carmel.alex at gmail.com, your version fails with utf8_strrev($string, true). It's something about spaces.

For example, you turn
This software was protected by 2000 patents since 2001
into
2001 ecnis stnetap2000 yb detcetorp saw erawtfos sihT

(note the "stnetap2000").

manfred at werkzeugH dot at (27-May-2008 12:35)

here is my version for strings with utf8-characters represented as numerical entities  (e.g. &#1234;)

function utf8_entities_strrev($str, $preserve_numbers = true)
{
  //split string into string-portions (1 byte characters, numerical entitiesor numbers)

  $parts=Array();
  while ($str)
  {
    if ($preserve_numbers && preg_match('/^([0-9]+)(.*)$/',$str,$m))
    {
      // number-flow
      $parts[]=$m[1];
      $str=$m[2];
    }
    elseif (preg_match('/^(\&#[0-9]+;)(.*)$/',$str,$m))
    {
      // numerical entity
      $parts[]=$m[1];
      $str=$m[2];
    }
    else
    {
      $parts[]=substr($str,0,1);
      $str=substr($str,1);
    }
  }

  $str=implode(array_reverse($parts),"");

  return $str;
}

Anonymous (18-Dec-2007 10:30)

MOD10, Modulus10 or also called LUHN10 will generate a valid check digit.

<?php
$inv = "34586";
echo $inv . checkdigit($inv);

// Outputs 345868

function checkdigit($num) {
$sum = 0;
$pos = 0;
$rev = strrev($num);
$len = strlen($num);
if ($len % 2 == 0) $len += 1;
while ($pos < $len) {
$odd = $rev[$pos] * 2;
if ($odd > 9) {
$odd -= 9;
}
$sum += $odd;
if ($pos != ($len - 2)) {
$sum += $rev[$pos +1];
}
$pos += 2;
}
return ((floor($sum/10) + 1) * 10 - $sum) % 10;
}
?>

carmel.alex at gmail.com (21-Dec-2006 06:38)

to lwc at mytrashmail dot com,  take it easy.

function utf8_strrev($str, $reverse_numbers = true){
    $pattern = $reverse_numbers ? '/./us' : '/(\d+)?./us';
    preg_match_all($pattern, $str, $ar);
    return join('',array_reverse($ar[0]));
}

lwc at mytrashmail dot com (14-Oct-2006 12:01)

just as well for UTF-8 usages = I meant also for NONE UTF-8 usages (to keep the numbers unchanged)

lwc at mytrashmail dot com (13-Oct-2006 09:35)

/*
Here's a function that adds to carmel.alex's utf-8 encoding support the ability NOT to reverse numbers (for example when you output a phrase as a parameter for a SWF file that can't handle RTL languages itself, but obviously any numbers should remain the same as in the original phrase).

Note that it can be used just as well for UTF-8 usages if you want the numbers to remain intact:
*/

function utf8_strrev($str, $reverse_numbers) {
  preg_match_all('/./us', $str, $ar);
  if ($reverse_numbers)
    return join('',array_reverse($ar[0]));
  else {
      $temp = array();
      foreach ($ar[0] as $value) {
         if (is_numeric($value) && !empty($temp[0]) && is_numeric($temp[0])) {
            foreach ($temp as $key => $value2) {
               if (is_numeric($value2))
                 $pos = ($key + 1);
               else
                  break;
            }
            $temp2 = array_splice($temp, $pos);
            $temp = array_merge($temp, array($value), $temp2);
         } else
            array_unshift($temp, $value);
      }
      return implode('', $temp);
  }
}

// "It says this site is copyrighted just from 2001" (in Hebrew)
$str = "???? ????? ??? ???? ??????? ?????? ?? ??? 2001";
// Reverse everything
$str_blind_reverse = utf8_strrev($str, true);
// Reverse everything but don't change the year 2001 to 1002...
$str_logical_reverse = utf8_strrev($str, false);

carmel.alex at gmail.com (28-Feb-2006 08:54)

This function support utf-8 encoding

function utf8_strrev($str){
    preg_match_all('/./us', $str, $ar);
    return join('',array_reverse($ar[0]));
}

tex at i18nguy dot com (23-Aug-2005 05:36)

Just a correction to the previous commenter. In ISO 8859-15, the Euro is 0xA4 (164 decimal). It is a 1 byte character.

MagicalTux at FF dot st (12-May-2005 02:20)

I will make Screend at hf dot webex dot com's comment more clear and understandable.

strrev only works for singlebyte character-sets. Multibytes charactersets are not compatibles with strrev.

US-ASCII and ISO-8859-1 are compatible with strrev, however BIG5, SJIS, UTF-8 aren't.

Despite what you can think, ISO-8859-15 *is* multibyte (the euro symbol - - is coded on two bytes).

There's no mb_strrev function in PHP, so you can't strrev() a multibyte string. Try to convert it to something else with iconv() if it can be represented in a singlebyte character set.

avarab at gmail dot com (07-May-2005 08:53)

strrev() can be very useful in cases where it makes more sense to do something from the end of a string rather than the beginning (well duh!) such as apply certain regular expressions. Here's a small function to add commas to numbers that works in such a way.

<?php
echo commafy("1500000.1254"); // prints 1,500,000.1254

function commafy($_) {
        return strrev( (string)preg_replace( '/(\d{3})(?=\d)(?!\d*\.)/', '$1,' , strrev( $_ ) ) );
}
?>

I originally wrote it in Perl, does it show? ;=)

Screend at hf dot webex dot com (31-Mar-2004 04:17)

this function can only reverse the 1-byte words,like english,it seems,using
<?php
$str=strrev("");
echo $str;
?>
do not get a right result.
but,you can change 2-bytes characters into a ASCLL,the converse it.