字符串函数
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strtolower

(PHP 4, PHP 5)

strtolower — 将字符串转化为小写

说明

string strtolower ( string $str )

将 string 中所有的字母字符转换为小写并返回。

注意 “字母” 与当前所在区域有关。例如，在默认的 “C” 区域，字符 umlaut-A（?）就不会被转换。

参数

str

输入字符串。

返回值

返回转换后的小写字符串。

范例

Example #1 strtolower() 范例

<?php
$str = "Mary Had A Little Lamb and She LOVED It So";
$str = strtolower($str);
echo $str; // 打印 mary had a little lamb and she loved it so
?>

注释

Note: 此函数可安全用于二进制对象。

参见

字符串函数
在线手册：中文 英文
PHP手册
PHP手册 - N: 将字符串转化为小写

用户评论:

on at niepodam dot pl (24-Oct-2011 03:23)

If the input string is in different language that server locale, then you should use mb_strtolower() function.

RCube (01-Apr-2011 12:57)

To convert an entire array to lower, I prefer this method;

<?php
function arraytolower(array $array, $round = 0){
  return unserialize(strtolower(serialize($array)));
}
?>

3 lines of code seem a lot less overhead than 10-40.
If there's any intrinsic problem with this method, please post it.

marcin at maydesign dot pl (22-Jun-2010 11:16)

strtolower(); doesn't work for polish chars

<?php strtolower("m?kA"); ?>
will return: m?ka;

the best solution - use mb_strtolower()

<?php mb_strtolower("m?kA",'UTF-8'); ?>
will return: m?ka

sanderwind at gmail dot com (11-Jun-2010 02:03)

Very easy way to only make the first character lowercase:

<?php
  function lcfirst($string) {
      $string{0} = strtolower($string{0});
      return $string;
  }
?>

ewertonp at hotmail dot com (30-Sep-2009 07:50)

Here is my solution to lowercase strings Latin strings with accents. In this case I've used Brazilian Portuguese locale:

<?PHP

setlocale(LC_ALL, 'pt_BR');

echo strtolower('??????');
// output: éá?úí?

echo ucfirst(strtolower('é?????'));
// output: ?á?úí?

?>

leha_grobov (26-Jun-2009 04:03)

the strtolower version to support most amount of languages including russian, french and so on:

<?php
function strtolower_utf8($string){
  $convert_to = array(
    "a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u",
    "v", "w", "x", "y", "z", "à", "á", "?", "?", "?", "?", "?", "?", "è", "é", "ê", "?", "ì", "í", "?", "?",
    "?", "?", "ò", "ó", "?", "?", "?", "?", "ù", "ú", "?", "ü", "?", "а", "б", "в", "г", "д", "е", "ё", "ж",
    "з", "и", "й", "к", "л", "м", "н", "о", "п", "р", "с", "т", "у", "ф", "х", "ц", "ч", "ш", "щ", "ъ", "ы",
    "ь", "э", "ю", "я"
  );
  $convert_from = array(
    "A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U",
    "V", "W", "X", "Y", "Z", "?", "?", "?", "?", "?", "?", "?", "?", "?", "?", "?", "?", "?", "?", "?", "?",
    "?", "?", "?", "?", "?", "?", "?", "?", "?", "?", "?", "?", "?", "А", "Б", "В", "Г", "Д", "Е", "Ё", "Ж",
    "З", "И", "Й", "К", "Л", "М", "Н", "О", "П", "Р", "С", "Т", "У", "Ф", "Х", "Ц", "Ч", "Ш", "Щ", "Ъ", "Ъ",
    "Ь", "Э", "Ю", "Я"
  );

  return str_replace($convert_from, $convert_to, $string);
}
?>

Khigashi (22-Jun-2009 10:53)

Here is my code, I made because of the accents contained in the latin languages [like the Portuguese of Brazil =)]

<?php
function deepLower($texto){
    //Letras minúsculas com acentos
    $texto = strtr($texto, "
    ?????????ABCDEFGHIJKLMNOPRSTUWYZQ
    XVЁЙЦУКЕНГШЩЗХЪФЫВАПРОЛДЖЭЯЧСМИТЬБЮ
    ???????????????????????
    ", "
    ????ńó???abcdefghijklmnoprstuwyzq
    xvёйцукенгшщзхъфывапролджэячсмитьбю
    ?àá??êèé??íì???òó??ùúü?
    ");
    return strtolower($texto);
}
?>

hans111 {AT} yahoo {DOT} com (13-May-2009 11:02)

Could be useful, if mb string library is not available for whatever the reason:
<?php
    function utf8_strtolower($string) {
        return utf8_encode(strtolower(utf8_decode($string)));
    }
##equally.....
    function utf8_ucfirst($string) {
        return utf8_encode(ucfirst(utf8_decode($string)));
    }
#.....etc...
?>
It has worked for me, just make sure you feed the functions with the proper encoded text (utf-8)

[These functions] only work when translation is between common characters in ISO 8859-1 and UTF-8, that means they will work well with western languages but not cyrillic or asian.

coder at bulgaria dot bg (04-Apr-2009 12:08)

for cyrillic and UTF 8 use  mb_convert_case

exampel

<?php
$string = "Австралия";
$string = mb_convert_case($string, MB_CASE_LOWER, "UTF-8");
echo $string;

//output is: австралия
?>

ghutix6 at gmail dot com (15-Mar-2009 09:50)

Here is function for working polish lower letters (plus example):

<?php
 
  function lower_pl($str)
   {
     return strtr($str, "?????????ABCDEFGHIJKLMNOPRSTUWYZQXV", "????ńó???abcdefghijklmnoprstuwyzqxv");
   }
 
  $word ="???TKO";
  $word = lower_pl ($word);

  echo ("<p>$word</p>");  
 
?>

This will turn into: <p>?ó?tko</p>.

dbers26 at gmail dot com (07-Jan-2009 09:34)

the function  arraytolower will create duplicate entries since keys are case sensitive. 

<?php
$array = array('test1' => 'asgAFasDAAd', 'TEST2' => 'ASddhshsDGb', 'TeSt3 '=> 'asdasda@asdadadASDASDgh');

$array = arraytolower($array);
?>
/*
Array
(
    [test1] => asgafasdaad
    [TEST2] => ASddhshsDGb
    [TeSt3] => asdasda@asdadadASDASDgh
    [test2] => asddhshsdgb
    [test3] => asdasda@asdadadasdasdgh
)
*/

I prefer this method

<?php
  function arraytolower($array, $include_leys=false) {
   
    if($include_leys) {
      foreach($array as $key => $value) {
        if(is_array($value))
          $array2[strtolower($key)] = arraytolower($value, $include_leys);
        else
          $array2[strtolower($key)] = strtolower($value);
      }
      $array = $array2;
    }
    else {
      foreach($array as $key => $value) {
        if(is_array($value))
          $array[$key] = arraytolower($value, $include_leys);
        else
          $array[$key] = strtolower($value);  
      }
    }
   
    return $array;
  }
?>

which when used like this

<?php
$array = $array = array('test1' => 'asgAFasDAAd', 'TEST2' => 'ASddhshsDGb', 'TeSt3 '=> 'asdasda@asdadadASDASDgh');

$array1 = arraytolower($array);
$array2 = arraytolower($array,true);

print_r($array1);
print_r($array2);
?>

will give output of

Array
(
    [test1] => asgafasdaad
    [TEST2] => asddhshsdgb
    [TeSt3] => asdasda@asdadadasdasdgh
)
Array
(
    [test1] => asgafasdaad
    [test2] => asddhshsdgb
    [test3] => asdasda@asdadadasdasdgh
)

s0urce at anonyme dot com (23-Oct-2008 11:05)

for someone who needs - arraytolower:

<?php
function arraytolower($array,$round = 0){
    foreach($array as $key => $value){
        if(is_array($value)) $array[strtolower($key)] =  $this->arraytolower($value,$round+1);
        else $array[strtolower($key)] = strtolower($value);
        }
        return $array;
    }
?>

converts the whole array in a levels. keys and values.

rodrigoATsistemasparainternetDOTcomDOTbr (10-Sep-2008 02:25)

<?php
function fullLower($str){
   // convert to entities
   $subject = htmlentities($str,ENT_QUOTES);
   $pattern = '/&([a-z])(uml|acute|circ';
   $pattern.= '|tilde|ring|elig|grave|slash|horn|cedil|th);/e';
   $replace = "'&'.strtolower('\\1').'\\2'.';'";
   $result = preg_replace($pattern, $replace, $subject);
   // convert from entities back to characters
   $htmltable = get_html_translation_table(HTML_ENTITIES);
   foreach($htmltable as $key => $value) {
      $result = ereg_replace(addslashes($value),$key,$result);
   }
   return(strtolower($result));
}

echo fullLower("? ? ? ? ???");

//results ? é ò ? úù?
//adapted from fullUpper on strtoupper manual
?>

concepton at gmail dot com (11-Aug-2008 05:50)

comment to "alexfort at list dot ru"

i think better to use this one

<?php
function strtolower_ru($text) {
    $alfavitlover = array('ё','й','ц','у','к','е','н','г', 'ш','щ','з','х','ъ','ф','ы','в', 'а','п','р','о','л','д','ж','э', 'я','ч','с','м','и','т','ь','б','ю');
    $alfavitupper = array('Ё','Й','Ц','У','К','Е','Н','Г', 'Ш','Щ','З','Х','Ъ','Ф','Ы','В', 'А','П','Р','О','Л','Д','Ж','Э', 'Я','Ч','С','М','И','Т','Ь','Б','Ю');

    return str_replace($alfavitupper,$alfavitlover,strtolower($text));
}
?>

alexfort at list dot ru (04-Aug-2008 01:43)

<?php
//solution to the Cyrillic and uft-8
function strtolower_Cyrillic($word) {
    $alfavitlover = explode(',', 'ё,й,ц,у,к,е,н,г,ш,щ,з,х,ъ,ф,ы,
    в,а,п,р,о,л,д,ж,э,я,ч,с,м,и,т,ь,б,ю');
    $alfavitupper = explode(',', 'Ё,Й,Ц,У,К,Е,Н,Г,Ш,Щ,З,Х,Ъ,Ф,Ы,
    В,А,П,Р,О,Л,Д,Ж,Э,Я,Ч,С,М,И,Т,Ь,Б,Ю');
    for($wr=0;$wr<=count($alfavitlover);$wr++) {
        $word = str_replace($alfavitupper[$wr], $alfavitlover[$wr], $word);
    }
    return $word;
}
echo strtolower_Cyrillic('СаШа+МаШа');
?>

tushar at sel2in dot com (28-Jul-2008 04:57)

Quick and works for accented characters like á

Tested on linux and win apache+php5

<?php
function strtolower2($s){
    $ln = strlen($s);
    $ln1 = $ln -1;
    for($i=0; $i < $ln; $i++){
        $k = ord(substr($s, $i, 1));
        if($k>=65 && $k <= 90){
            if($i > 0){
                $l1 = substr($s, 0, $i);
            }else{
                $l1 ='';
            }
            $l1 = $l1 . chr($k+32);
            if($i < $ln1){
                $l1 = $l1 . substr($s, $i  + 1);
            }
            $s = $l1;

        }
    }
    return $s;
}
?>

Piotr (10-Mar-2008 09:24)

///charset=iso-8859-2
 function strtolower_iso8592($string)
    {
        $low=array("ˇ" => "±", "?" => "?", "?" => "?", "?" => "?", "?" => "ó", "?" => "?", "?" => "?", "?" => "?", "?" => "ń");
        return strtolower(strtr($string,$low));
       
       
       
    }

toringe at infostill dot com (25-Oct-2007 11:27)

This will work for all languages using ISO8859_1 - more code than many other but fast.

<?php
function strtolower_iso8859_1($s){
    $i = strlen($s);
    while ($i > 0) {
        --$i;
        $c =ord($s[$i]);
        if (($c & 0xC0) == 0xC0) {
            // two most significante bits on
            if (($c != 215) and ($c != 223)){ // two chars OK as is
                // to get lowercase set 3. most significante bit if needed:
                $s[$i] = chr($c | 0x20);
            }
        }
    }
    return strtolower($s);
}   
?>

patricia at steuerungb dot de (17-Oct-2007 02:29)

When you're not sure, how the current locale is set, you might find the following function useful. It's strtolower for utf8-formatted text:

<?php
function strtolower_utf8($inputString) {
    $outputString    = utf8_decode($inputString);
    $outputString    = strtolower($outputString);
    $outputString    = utf8_encode($outputString);
    return $outputString;
}
?>

It's not suitable for every occasion, but it surely gets in handy. I use it for lowering German 'Umlauts' like ? and ?.

mr dot blober at gmail dot com (16-Jun-2007 07:39)

simple example for Polish characters
<?php
function strtolower_pl($str)
{
return strtr(strtolower($str), '[?????????]', '[????ńó???]');
}
?>

rok dot kralj at gmail dot com (04-Jun-2007 07:49)

Slovenian characters

<?php
    function strtolower_slovenian($string)
    {
        $low=array("?" => "?", "?" => "?", "?" => "?");
        return strtolower(strtr($string,$low));
    }

?>

marco at recchiuti dot it (22-May-2007 08:43)

Maybe it is not so elegant, but it Works.
It's just a fast Idea and it is what I need.
Any hacks for other characters (link !, ? etc etc) should help.

function RemoveShouting($string)
{
     $frase = "";   
     $astri = explode(".", $string);
     foreach ($astri as $elem)
    $frase .= " ".ucfirst(trim(strtolower($elem))).". ";
      
    return trim($frase);
}

Cheers!
M

mario dot kostelac at gmail dot com (29-Apr-2007 12:42)

This is strtolower function for Croatian characters:
function strToLowerCro($string){
    $string = strtolower($string);
    $patterns[0] = '/?/';
    $patterns[1] = '/?/';
    $patterns[2] = '/?/';
    $patterns[3] = '/?/';
    $patterns[4] = '/?/';
    $replacements[0] = '?';
    $replacements[1] = '?';
    $replacements[2] = '?';
    $replacements[3] = '?';
    $replacements[4] = '?';
    $string = preg_replace($patterns, $replacements, $string);
    return $string;
}
Enjoy...

HQ063 (31-Mar-2007 08:37)

Similar to last function, but for spanish
    function strtolower_es($string)
    {
        $low=array("?" => "á", "?" => "é", "?" => "í", "?" => "ó", "?" => "ú", "?" => "ü", "?" => "?");
        return strtolower(strtr($string,$low));
    }

Din?er Akay (20-Dec-2006 10:32)

Turkish Character
<?php
    function strtolower_tr($string)
    {
        $low=array("?" => "ü", "?" => "?", "?" => "?", "?" => "?", "?" => "?", "?" => "i", "I" => "?");
        return strtolower(strtr($string,$low));
    }

?>

Enzo_01 at abv dot bg (07-Nov-2006 07:31)

two functions what works with cyrilic text

function cyr_strtolower($a) {
        $offset=32;
        $m=array();
        for($i=192;$i<224;$i++)$m[chr($i)]=chr($i+$offset);
        return strtr($a,$m);
}
function cyr_strtoupper($a) {
        $offset=32;
        $m=array();
        for($i=192;$i<224;$i++)$m[chr($i+$offset)]=chr($i);
        return strtr($a,$m);
}

ex:
 cyr_strtoupper("абвгде"); // АБВГДЕ
 cyr_strtolower("АБВГДЕ"); // абвгде

eduardor2k at redr2k dot com (08-Aug-2006 10:34)

I changed it a bit and i found that it's better to put everything in lowercase, and rebuild the text the same way a teacher corrects a text, for now it only checks that the first letter after a point "." must be
in upper case.

    function RemoveShouting($string)
    {
        $string = strtolower(trim($string));
      
        for($i=0;$i<strlen($string);$i++){
      
            if($i==0){$string[$i] = strtoupper($string[$i]);}
          
            if($string[$i] == "."){
                while($string[$i+1] == " "){
                    $i++;
                }
                $string[$i+1] = strtoupper($string[$i+1]);
                $i++;
            }
        }
      
    return $string;
    }

this function would change:
Hi mi name is PETER. SOME TIMES I FORGOT TO DISABLE CAPS LOCK.

into:

Hi mi name is peter. Some times i forgot to disable caps lock.

spiceee ddotty spiceee com (07-Mar-2006 12:53)

If you ever need to strtolower a string with href tags on it and doesn't want to mess with the characters inside a tag, this is for you.

<?php

function loweroutsidetags ($str) {
    $chars = preg_split ("//", $str);
    $tolower = true;
    $str = '';

    foreach ($chars as $k) {
        if ($k == '<') { $tolower = false; }
        if ($tolower) { $k = strtolower ($k); }
        $str .= $k;   
        if ($k == '>') { $tolower = true; }
    }
    return $str;
}

?>

this:
echo loweroutsidetags('aALalala <a href="?q=CASEsENSITIVINESSinURLSareSTUPID">')

will give:
aalalala <a href="?q=CASEsENSITIVINESSinURLSareSTUPID">

red at iklanumum dot com (24-Feb-2006 02:43)

I've seen this as a common use from script developers, so I would like to share the alternative way to compare 2 string (CASE INSENSITIVE) without using strtolower for faster process.

Use strcasecmp() for comparison purpose rather than comparing uncertain case of 2 string variables, because strcasecmp() is approximately 60% faster, moreover, the greater its string length the greater the difference,!
Ex. case :
$var1;    -> could be a mixture of upper & lower case
$var2;    -> could be a mixture of upper & lower case

To compare whether $var1 is exactly the same as $var2 (case insensitive manner):
Use -> if (strcasecmp($var1,$var2)==0)
rather than -> if (strtolower($var1)==strtolower($var2))

Patrick (19-Jan-2006 06:57)

If you're considering using the below unhtmlentities function from phpContrib, I would suggest this one as an alternative:

<?php
function unhtmlentities($string)
{
   // replace numeric entities
   $string = preg_replace('~&#x([0-9a-f]+);~ei', 'chr(hexdec("\\1"))', $string);
   $string = preg_replace('~&#([0-9]+);~e', 'chr(\\1)', $string);
   // replace literal entities
   $trans_tbl = get_html_translation_table(HTML_ENTITIES);
   $trans_tbl = array_flip($trans_tbl);
   return strtr($string, $trans_tbl);
}
?>

That was copied exactly from the html_entity_decode manual page.  It'll handle numeric entities correctly, the below function won't.

fackelkind (11-Jan-2006 08:03)

Nifty? :D

<?php
        function is_lowercase ($str){
                return ($str == strtolower ($str));
        }
?>

mhuggins57 at yahoo dot com (20-Jul-2005 12:04)

There's a ucfirst "function" to make the first character uppercase, but there's no "lcfirst" function to make the first character lowercase.  Here's my own code to accomplish this.

<?
function lcfirst($str) {
    return strtolower(substr($str, 0, 1)) . substr($str, 1);
}
?>

I found this particularly useful for generating XML nodes with the Reflection class.

kmcdermott at perimeterinstitute dot ca (08-Dec-2004 09:04)

To do case insensitive comparisons in a database, strtolower() can be a quick and dirty solution:

$Sql = "SELECT * FROM tablename WHERE LOWER(column_name) = '".strtolower($my_var)."'";

phpContrib (A T) esurfers d o t c o m (24-Sep-2004 07:07)

<?php

$b=html_entity_decode(strtolower(htmlentities($a)));

?>

will convert to lowercase most accented vocals
(it will convert into &Agrave; into &agrave; into )

This is not fast and clean code, it is just a quick oneliner to help you if you need a quick way to do it



Users with older versions of PHP can use:
$b=unhtmlentities(strtolower(htmlentities($a)));

// with unhtmlentities() as defined in the html_entity_decode() manual page:

function unhtmlentities ($string) {
    $trans_tbl =get_html_translation_table (HTML_ENTITIES );
    $trans_tbl =array_flip ($trans_tbl );
    return strtr ($string ,$trans_tbl );
}

bkimble at ebaseweb dot com (20-Jan-2003 06:39)

Heres a small function I wrote to stop people from submitting data that is ALL IN CAPS SO THEY CAN GET MORE ATTENTION THAT THE REST OF THE USER SUBMITTED DATA on my website :) If you can make it better, by all means do so. This function splits up words delimited by a space, and makes only the first letter of each word capitalized. You can easily modify it so it's only the very first word of the string. I've also added some exceptions so you don't make things like roman numerals look like "Iii" or "Xcmii" or something.

function RemoveShouting($string)
{
 $lower_exceptions = array(
        "to" => "1", "a" => "1", "the" => "1", "of" => "1"
 );
 
 $higher_exceptions = array( 
        "I" => "1", "II" => "1", "III" => "1", "IV" => "1", 
        "V" => "1", "VI" => "1", "VII" => "1", "VIII" => "1",
        "XI" => "1", "X" => "1"
 );
 
 $words = split(" ", $string);
 $newwords = array();
 foreach ($words as $word)
 {
  if (!$higher_exceptions[$word]) $word = strtolower($word);
  if (!$lower_exceptions[$word]) $word[0] = strtoupper($word[0]);
  array_push($newwords, $word);
 }
 return join(" ", $newwords);
}

BK

tty01_at_rambler_dot_ru (20-Sep-2002 03:58)

Another solution for Double-Byte-Characters, based on iconv() functions, not sensible to the current locale, works on win32.

/* Converts charset */
function myConvertCharset($str, $from, $to)
{
    if(@function_exists('iconv'))
    {
        return iconv($from, $to, $str);
    }
    else if(@function_exists('recode_string'))
    {
        return recode_string($from . '..'  . $to, $str);
    }
    else
    {
        print "function iconv not exists";
        return $str;
    }
}
/* Converts a string to lowercase */
function my_strtolower($s)
{
    $t = "windows-1251";
    $d = "UTF-8";
    return myConvertCharset(strtolower(myConvertCharset($s, $d, $t)), $t, $d);
}

print my_strtolower("СЛОВО  Uppercase");

(13-Sep-2002 01:17)

This function is sensible to the current locale, namely the LC_CTYPE category (the default LC_CTYPE category is set from the LANG environment variable or by an explicit LC_CTYPE setting, but it can be overriden by the LC_ALL environment setting). If no locale setting is done in the enironment, the default locale will be C, for which the lowercase/uppercase conversion is based on the default character set of the system: this may convert only ASCII letters, or also ISO-8859-1 letters depending on the system...