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MySQL字段長度是這樣統計的:所有字符都被認為是1個字符
一派護法 十九級
1樓 發表于:2015-2-14 22:25
比如“正體中文abc”被認為是7個字符,“我I你you”被認為是六個字符,就連標點符號也被認為是一個字符。所有的漢字都算一個字符而非兩個。
因此把“正體中文abc”插入一個varchar(7)的字段是可以的,但插入“正體中文abc,”就不行了,雖然記錄能成功插入但會把末尾的逗號吞掉
一派護法 十九級
2樓 發表于:2015-2-14 22:25
<article class="content">
    <h1>For PHP</h1>
    <section>
     <h2>Using strlen</h2>
     <p>
     <?php
     $strs = array();
     $strs[0] = "simple";
     $strs[1] = "¿español?";
     $strs[2] = "estómago; ¡díficil!";
     $strs[3] = "這是一段測試內容。";
     $strs[4] = "這是另1段測試內容";
     $strs[5] = "台灣正,體中文";
     $strs[6] = "文";
     $strs[7] = ",";
     $strs[8] = "ñ";
     $strs[9] = "¿";
     $strs[10] = "?";
     
     foreach ($strs as $str) {
         $n = strlen($str);
         if ($n == 1) {
            echo "String '$str' has <b>1</b> character.<br>";
         } else {
            echo "String '$str' has <b>$n</b> characters.<br>";
         }
     }
     ?></p>
    </section>
    <!-- end .content --></article>

For PHP Using strlen String 'simple' has 6 characters.
String '¿español?' has 11 characters.
String 'estómago; ¡díficil!' has 22 characters.
String '這是一段測試內容。' has 27 characters.
String '這是另1段測試內容' has 25 characters.
String '台灣正,體中文' has 19 characters.
String '文' has 3 characters.
String ',' has 1 character.
String 'ñ' has 2 characters.
String '¿' has 2 characters.
String '?' has 1 character.


可見,對於PHP的strlen函數,把漢字當成了3個字符,西班牙語特殊字符(倒問號,倒感歎號,字母ñ,帶重音符號的字母)當成了2個字符,而英文字母和標點當成1個字符!
因此,不能用strlen函數來判斷字符串長度是否符合mysql的要求。

如果用戶輸入的內容包含html特殊字符,就需要用htmlspecialchars轉換,那麼字符就會多出幾個。不過mysql_real_escape_string函數不用管,mysql會自動將特殊字符轉換回來。
一派護法 十九級
3樓 發表于:2015-2-14 22:26
如果改用mb_strlen函數,問題就得到了解決。

echo "<br><br>";
     foreach ($strs as $str) {
         $n = mb_strlen($str);
         if ($n == 1) {
            echo "String '$str' has <i>actually</i> <b>1</b> character.<br>";
         } else {
            echo "String '$str' has <i>actually</i> <b>$n</b> characters.<br>";
         }
     }

String 'simple' has actually 6 characters.
String '¿español?' has actually 9 characters.
String 'estómago; ¡díficil!' has actually 19 characters.
String '這是一段測試內容。' has actually 9 characters.
String '這是另1段測試內容' has actually 9 characters.
String '台灣正,體中文' has actually 7 characters.
String '文' has actually 1 character.
String ',' has actually 1 character.
String 'ñ' has actually 1 character.
String '¿' has actually 1 character.
String '?' has actually 1 character.

因此可以在用戶輸入數據后,先進行htmlspecialchars編碼(如果需要的話),然後用mb_strlen函數對字符串長度進行比較,如果超出數據庫中設定的字段長度就提示錯誤就行了。
一派護法 十九級
4樓 發表于:2015-2-14 22:26
<h1>For JavaScript</h1>
    <section>
     <p>
     <script>
     var strs = [];
     strs[0] = "simple";
     strs[1] = "¿español?";
     strs[2] = "estómago; ¡díficil!";
     strs[3] = "這是一段測試內容。";
     strs[4] = "這是另1段測試內容";
     strs[5] = "台灣正,體中文";
     strs[6] = "文";
     strs[7] = ",";
     strs[8] = "ñ";
     strs[9] = "¿";
     strs[10] = "?";
     
     for (var i = 0; i < strs.length; i++) {
         var n = strs[i].length;
         if (n == 1) {
            document.write("String '" + strs[i] + "' has <b>1</b> character.<br>");
         } else {
            document.write("String '" + strs[i] + "' has <b>" + n + "</b> characters.<br>");
         }
     }
     </script>
     </p>
    </section>

For JavaScript String 'simple' has 6 characters.
String '¿español?' has 9 characters.
String 'estómago; ¡díficil!' has 19 characters.
String '這是一段測試內容。' has 9 characters.
String '這是另1段測試內容' has 9 characters.
String '台灣正,體中文' has 7 characters.
String '文' has 1 character.
String ',' has 1 character.
String 'ñ' has 1 character.
String '¿' has 1 character.
String '?' has 1 character.


因此對於javascript,直接使用str.length就行了,得到的就是正確的結果。
一派護法 十九級
5樓 發表于:2015-2-14 22:26
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>Untitled Document</title>
<style type="text/css">
<!--
body {
    font: 100%/1.4 Verdana, Arial, Helvetica, sans-serif;
    background-color: #42413C;
    margin: 0;
    padding: 0;
    color: #000;
}
/* ~~ Element/tag selectors ~~ */
ul, ol, dl { /* Due to variations between browsers, it's best practices to zero padding and margin on lists. For consistency, you can either specify the amounts you want here, or on the list items (LI, DT, DD) they contain. Remember that what you do here will cascade to the .nav list unless you write a more specific selector. */
    padding: 0;
    margin: 0;
}
h1, h2, h3, h4, h5, h6, p {
    margin-top: 0;     /* removing the top margin gets around an issue where margins can escape from their containing block. The remaining bottom margin will hold it away from any elements that follow. */
    padding-right: 15px;
    padding-left: 15px; /* adding the padding to the sides of the elements within the blocks, instead of the block elements themselves, gets rid of any box model math. A nested block with side padding can also be used as an alternate method. */
}
a img { /* this selector removes the default blue border displayed in some browsers around an image when it is surrounded by a link */
    border: none;
}
/* ~~ Styling for your site's links must remain in this order - including the group of selectors that create the hover effect. ~~ */
a:link {
    color: #42413C;
    text-decoration: underline; /* unless you style your links to look extremely unique, it's best to provide underlines for quick visual identification */
}
a:visited {
    color: #6E6C64;
    text-decoration: underline;
}
a:hover, a:active, a:focus { /* this group of selectors will give a keyboard navigator the same hover experience as the person using a mouse. */
    text-decoration: none;
}
/* ~~ This fixed width container surrounds all other blocks ~~ */
.container {
    width: 960px;
    background-color: #FFFFFF;
    margin: 0 auto; /* the auto value on the sides, coupled with the width, centers the layout */
}
/* ~~ The header is not given a width. It will extend the full width of your layout. ~~ */
header {
    background-color: #ADB96E;
}
/* ~~ These are the columns for the layout. ~~

1) Padding is only placed on the top and/or bottom of the block elements. The elements within these blocks have padding on their sides. This saves you from any "box model math". Keep in mind, if you add any side padding or border to the block itself, it will be added to the width you define to create the *total* width. You may also choose to remove the padding on the element in the block element and place a second block element within it with no width and the padding necessary for your design.

2) No margin has been given to the columns since they are all floated. If you must add margin, avoid placing it on the side you're floating toward (for example: a right margin on a block set to float right). Many times, padding can be used instead. For blocks where this rule must be broken, you should add a "display:inline" declaration to the block element's rule to tame a bug where some versions of Internet Explorer double the margin.

3) Since classes can be used multiple times in a document (and an element can also have multiple classes applied), the columns have been assigned class names instead of IDs. For example, two sidebar blocks could be stacked if necessary. These can very easily be changed to IDs if that's your preference, as long as you'll only be using them once per document.

4) If you prefer your nav on the left instead of the right, simply float these columns the opposite direction (all left instead of all right) and they'll render in reverse order. There's no need to move the blocks around in the HTML source.

*/
.sidebar1 {
    float: right;
    width: 180px;
    background-color: #EADCAE;
    padding-bottom: 10px;
}
.content {
    padding: 10px 0;
    width: 780px;
    float: right;
}

/* ~~ This grouped selector gives the lists in the .content area space ~~ */
.content ul, .content ol {
    padding: 0 15px 15px 40px; /* this padding mirrors the right padding in the headings and paragraph rule above. Padding was placed on the bottom for space between other elements on the lists and on the left to create the indention. These may be adjusted as you wish. */
}

/* ~~ The navigation list styles (can be removed if you choose to use a premade flyout menu like Spry) ~~ */
nav ul{
    list-style: none; /* this removes the list marker */
    border-top: 1px solid #666; /* this creates the top border for the links - all others are placed using a bottom border on the LI */
    margin-bottom: 15px; /* this creates the space between the navigation on the content below */
}
nav li {
    border-bottom: 1px solid #666; /* this creates the button separation */
}
nav a, nav a:visited { /* grouping these selectors makes sure that your links retain their button look even after being visited */
    padding: 5px 5px 5px 15px;
    display: block; /* this gives the link block properties causing it to fill the whole LI containing it. This causes the entire area to react to a mouse click. */
    width: 160px;  /*this width makes the entire button clickable for IE6. If you don't need to support IE6, it can be removed. Calculate the proper width by subtracting the padding on this link from the width of your sidebar container. */
    text-decoration: none;
    background-color: #C6D580;
}
nav a:hover, nav a:active, nav a:focus { /* this changes the background and text color for both mouse and keyboard navigators */
    background-color: #ADB96E;
    color: #FFF;
}

/* ~~ The footer ~~ */
footer {
    padding: 10px 0;
    background-color: #CCC49F;
    position: relative;/* this gives IE6 hasLayout to properly clear */
    clear: both; /* this clear property forces the .container to understand where the columns end and contain them */
}

/*HTML 5 support - Sets new HTML 5 tags to display:block so browsers know how to render the tags properly. */
header, section, footer, aside, article, figure {
    display: block;
}
-->
</style><!--[if lt IE 9]>
<script src="http://html5shiv.googlecode.com/svn/trunk/html5.js"></script>
<![endif]--></head>

<body>

<div class="container">
  <header>
    <a href="#"><img src="" alt="Insert Logo Here" width="180" height="90" id="Insert_logo" style="background-color: #C6D580; display:block;" /></a>
  </header>
  <div class="sidebar1">
  <nav>
    <ul>
      <li><a href="#">Link one</a></li>
      <li><a href="#">Link two</a></li>
      <li><a href="#">Link three</a></li>
      <li><a href="#">Link four</a></li>
    </ul>
    </nav>
    <aside>
      <p> The above links demonstrate a basic navigational structure using an unordered list styled with CSS. Use this as a starting point and modify the properties to produce your own unique look. If you require flyout menus, create your own using a Spry menu, a menu widget from Adobe's Exchange or a variety of other javascript or CSS solutions.</p>
      <p>If you would like the navigation along the top, simply move the ul to the top of the page and recreate the styling.</p>
    </aside>
  <!-- end .sidebar1 --></div>
  <article class="content">
    <h1>For PHP</h1>
    <section>
     <h2>Using strlen</h2>
     <p>
     <?php
     $strs = array();
     $strs[0] = "simple";
     $strs[1] = "¿español?";
     $strs[2] = "estómago; ¡díficil!";
     $strs[3] = "這是一段測試內容。";
     $strs[4] = "這是另1段測試內容";
     $strs[5] = "台灣正,體中文";
     $strs[6] = "文";
     $strs[7] = ",";
     $strs[8] = "ñ";
     $strs[9] = "¿";
     $strs[10] = "?";
     
     foreach ($strs as $str) {
         $n = strlen($str);
         if ($n == 1) {
            echo "String '$str' has <b>1</b> character.<br>";
         } else {
            echo "String '$str' has <b>$n</b> characters.<br>";
         }
     }
     
     ?></p>
     <h2>Using mb_strlen</h2>
     <p>
     <?php
     foreach ($strs as $str) {
         $n = mb_strlen($str);
         if ($n == 1) {
            echo "String '$str' has <i>actually</i> <b>1</b> character.<br>";
         } else {
            echo "String '$str' has <i>actually</i> <b>$n</b> characters.<br>";
         }
     }
     
     
     ?></p>
    </section>
    <h1>For JavaScript</h1>
    <section>
     <p>
     <script>
     var strs = [];
     strs[0] = "simple";
     strs[1] = "¿español?";
     strs[2] = "estómago; ¡díficil!";
     strs[3] = "這是一段測試內容。";
     strs[4] = "這是另1段測試內容";
     strs[5] = "台灣正,體中文";
     strs[6] = "文";
     strs[7] = ",";
     strs[8] = "ñ";
     strs[9] = "¿";
     strs[10] = "?";
     
     for (var i = 0; i < strs.length; i++) {
         var n = strs[i].length;
         if (n == 1) {
            document.write("String '" + strs[i] + "' has <b>1</b> character.<br>");
         } else {
            document.write("String '" + strs[i] + "' has <b>" + n + "</b> characters.<br>");
         }
     }
     </script>
     </p>
    </section>
    <!-- end .content --></article>
  <footer>
    <p>This footer contains the declaration position:relative; to give Internet Explorer 6 hasLayout for the footer and cause it to clear correctly. If you're not required to support IE6, you may remove it.</p>
    <address>
      Address Content
    </address>
  </footer>
  <!-- end .container --></div>
</body>
</html>
一派護法 十九級
6樓 發表于:2015-2-14 22:26
總而言之,為了和MySQL數據庫的字符串長度計算機制保持一致,在JavaScript中應該直接使用.length方法,而在PHP中則需要用mb_strlen函數。

順便提一下,PHH中截取子字符串也可以用mb_substr函數,避免出現亂碼。
一派護法 十九級
7樓 發表于:2015-2-24 18:33
為了兼容各種服務器,使用mb_strlen之前,最好執行一下:
mb_internal_encoding("UTF-8");
設置mbstring庫處理的默認字符集

我發現有的服務器上運行echo mb_strlen("漢字");輸出的結果還是6
一派護法 十九級
8樓 發表于:2015-2-25 17:19
還有一個更簡單的方法:使用表單控件的maxlength屬性,其單位與MySQL中的完全一樣。
<label for="textfield">Text Field:</label>
<input name="textfield" type="text" id="textfield" maxlength="6">
<label for="textarea"><br>
Text Area:</label>
<textarea name="textarea" id="textarea" style="margin-top:5px" maxlength="10"></textarea>
在第二個大文本框中,可以輸入“ab額as額ds啊啊”,剛好是10個字符。
一派護法 十九級
9樓 發表于:2015-2-25 17:21
不过,最好還是在服務器端表單處理程序中檢查一下字符串長度,以免用戶輸入HTML特殊符號,比如“<”而導致bug。比如在HTML中“<”會被編碼為&lt;,這樣一個<在數據庫中就是存儲的是4個字符而非1個。

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作者:巨大八爪鱼
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