PHP - Manual: strtolower

2024-05-03

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strtolower

(PHP 4, PHP 5, PHP 7, PHP 8)

strtolower — 将字符串转化为小写

说明

strtolower(string $string): string

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（ä）就不会被转换。

参数

string: 输入字符串。

返回值

返回转换后的小写字符串。

范例

示例 #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

注意: 此函数可安全用于二进制对象。

参见

strtoupper() - 将字符串转化为大写
ucfirst() - 将字符串的首字母转换为大写
ucwords() - 将字符串中每个单词的首字母转换为大写
mb_strtolower() - 使字符串小写

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User Contributed Notes 16 notes

down

111

marcin at maydesign dot pl ¶

11 years ago


strtolower(); doesn't work for polish chars


<?php strtolower("mĄkA"); ?>

will return: mĄka;


the best solution - use mb_strtolower()


<?php mb_strtolower("mĄkA",'UTF-8'); ?>

will return: mąka

down

helvete at bahno dot net ¶

7 years ago


It is worth noting that 
<?php 
var_dump(strtolower(null))
?>
returns: 
string(0) ""

down

coder at bulgaria dot bg ¶

13 years ago


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

?>

down

dbers26 at gmail dot com ¶

13 years ago


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

)

down

rodrigoATsistemasparainternetDOTcomDOTbr ¶

13 years ago


<?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("Ã É Ò Õ ÚÙÛ");

//results ã é ò õ úùû
//adapted from fullUpper on strtoupper manual
?>

down

patricia at steuerungb dot de ¶

14 years ago


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 ä and ö.

down

rok dot kralj at gmail dot com ¶

15 years ago


Slovenian characters

<?php
    function strtolower_slovenian($string)
    {
        $low=array("Č" => "č", "Ž" => "ž", "Š" => "š");
        return strtolower(strtr($string,$low));
    }

?>

down

bkimble at ebaseweb dot com ¶

19 years ago


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

down

marco at recchiuti dot it ¶

15 years ago


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

down

Patrick ¶

16 years ago


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.

down

-1

mhuggins57 at yahoo dot com ¶

16 years ago


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.

down

-3

RCube ¶

11 years ago


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.

down

-3

kmcdermott at perimeterinstitute dot ca ¶

17 years ago


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)."'";

down

-7

leha_grobov ¶

12 years ago


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", "â", "ã", "ä", "å", "æ", "ç", "è", "é", "ê", "ë", "ì", "í", "î", "ï", 

    "ð", "ñ", "ò", "ó", "ô", "õ", "ö", "ø", "ù", "ú", "û", "ü", "ý", "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", "À", "Á", "Â", "Ã", "Ä", "Å", "Æ", "Ç", "È", "É", "Ê", "Ë", "Ì", "Í", "Î", "Ï", 

    "Ð", "Ñ", "Ò", "Ó", "Ô", "Õ", "Ö", "Ø", "Ù", "Ú", "Û", "Ü", "Ý", "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);

}

?>

down

-7

spiceee ddotty spiceee com ¶

16 years ago


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">

down

-11

Daniel Klein ¶

6 years ago


When the locale is set to "utf8" or "C" I can't get strtolower() to convert accented characters encoded as UTF-8, so here is my workaround.

<?php
function tolower($string) {
  if ($old_locale = setlocale(LC_CTYPE, 0)) {
    // 'fr_FR.ISO-8859-1' for *nix, 'French_France.1252' fallback for Windows
    if ($newlocale = setlocale(LC_CTYPE, 'fr_FR.ISO-8859-1', 'French_France.1252')) {
      preg_match('/\.(?<encoding>.+)$/', $newlocale, $match);
      $string = utf8_encode(strtolower(utf8_decode($string)));
    }
    setlocale(LC_CTYPE, $old_locale);
  }
  return $string;
}

print(tolower('DÉJÀ-VU'));  // prints déjà-vu
?>

Change the language-country codes if you want some language other than French.

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官方地址：https://www.php.net/manual/en/function.strtolower.php

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PHP官方手册 - 互联网笔记

strtolower

说明

参数

返回值

范例

注释

参见

User Contributed Notes 16 notes