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  • strtolower()

    (PHP 4, PHP 5, PHP 7)

    将字符串转化为小写

    说明

    strtolower (string $string ) : string

    $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

    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

    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
    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
    ?>
    It is worth noting that 
    <?php 
    var_dump(strtolower(null))
    ?>
    returns: 
    string(0) ""
    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
    )
    <?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($result));
    }
    echo fullLower("Ã É Ò Õ ÚÙÛ");
    //results ã é ò õ úùû
    //adapted from fullUpper on strtoupper manual
    ?>
    When you're not sure, how the current locale is set, you might find the following function useful. It's strtolower for utf8-formatted text:
    <?php
    function strtolower_utf8($inputString) {
      $outputString  = utf8_decode($inputString);
      $outputString  = strtolower($outputString);
      $outputString  = utf8_encode($outputString);
      return $outputString;
    }
    ?>
    It's not suitable for every occasion, but it surely gets in handy. I use it for lowering German 'Umlauts' like ä and ö.
    Slovenian characters
    <?php
      function strtolower_slovenian($string)
      {
        $low=array("Č" => "č", "Ž" => "ž", "Š" => "š");
        return strtolower(strtr($string,$low));
      }
    ?>
    If you're considering using the below unhtmlentities function from phpContrib, I would suggest this one as an alternative:
    <?php
    function unhtmlentities($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, $trans_tbl);
    }
    ?>
    That was copied exactly from the html_entity_decode manual page. It'll handle numeric entities correctly, the below function won't.
    Maybe it is not so elegant, but it Works.
    It's just a fast Idea and it is what I need.
    Any hacks for other characters (link !, ? etc etc) should help.
    function RemoveShouting($string)
    {
       $frase = "";  
       $astri = explode(".", $string);
       foreach ($astri as $elem)
      $frase .= " ".ucfirst(trim(strtolower($elem))).". ";
        
      return trim($frase);
    }
    Cheers!
    M
    There's a ucfirst "function" to make the first character uppercase, but there's no "lcfirst" function to make the first character lowercase. Here's my own code to accomplish this.
    <?
    function lcfirst($str) {
      return strtolower(substr($str, 0, 1)) . substr($str, 1);
    }
    ?>
    I found this particularly useful for generating XML nodes with the Reflection class.
    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(" ", $newwords);
    }
    BK
    the strtolower version to support most amount of languages including russian, french and so on:
    <?php
    function strtolower_utf8($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);
    }
    ?>
    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)."'";
    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.
    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 $str;
    }
    ?>
    this: 
    echo loweroutsidetags('aALalala <a href="?q=CASEsENSITIVINESSinURLSareSTUPID">')
    will give:
    aalalala <a href="?q=CASEsENSITIVINESSinURLSareSTUPID">
    When the locale is set to "utf8" or "C" I can't get strtolower() to convert accented characters encoded as UTF-8, so here is my workaround.
    <?php
    function tolower($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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