mariadb - php使用带where的SQL查不出数据

先上代码：

<code>php</code><code class="lang-php"><form method="post" action="<?php%20echo%20htmlspecialchars(%24_SERVER%5B" php_self>"> 
<input name="qname" type="text" class="textlable" id="lname" onfocus="if (value =='姓名'){value ='';}" onblur="if (value == ''){value='姓名';}" value="姓名">
<input name="qcont" type="submit" value="查询">
</form>
<?php if ($_SERVER["REQUEST_METHOD"] == "POST") {
     if ($_POST["qname"] =="姓名") {
     $nameErr = "请输入姓名";
     }else {
        $con = mysql_connect("localhost","root","123456");
if (!$con)
  {
  die('Could not connect: ' . mysql_error());
  }
    mysql_query("set names ’utf8’ ");  
    mysql_query("set character_set_client=utf8");  
    mysql_query("set character_set_results=utf8"); 
    mysql_select_db("gkweb", $con);
    $sql="select c_name,c_extension,c_mail from gk_contacts where c_name='".$_POST["qname"]."'";
    echo $sql;
    $result = mysql_query($sql);
    echo "<table align='center' class='altrowstable' id='alternatecolor'><tr>
<th>姓名</th>
<th>座机</th>
<th>电子邮件</th>
</tr>";
    echo 123;
while($row = mysql_fetch_array($result))
  {
  echo "<tr>";
  echo "<td>" . $row['c_name'] . "</td>";
  echo "<td>" . $row['c_extension'] . "</td>";
  echo "<td>" . $row['c_mail'] . "</td>";
  echo "</tr>";
  }
echo "";
mysql_close($con);
     }}
?>
</code>

不知道为什么只要使用了带where的sql进行查询就没有输出结果。
但是使用$sql="select c_name,c_extension,c_mail from gk_contacts"却能输出所有数据.
我也使用echo $sql;输出的SQL在数据库后台查询了，能输出结果。求大神告知是哪里写错了。
不知道怎么排版，求不嫌弃。谢谢
刚才有大神说可能是数据库字符编码的问题，可我数据库都是用的UTF8

<code>bash</code><code class="lang-bash">MariaDB [(none)]>  show variables like '%char%';
+--------------------------+----------------------------+
| Variable_name            | Value                      |
+--------------------------+----------------------------+
| character_set_client     | utf8                       |
| character_set_connection | utf8                       |
| character_set_database   | utf8                       |
| character_set_filesystem | binary                     |
| character_set_results    | utf8                       |
| character_set_server     | utf8                       |
| character_set_system     | utf8                       |
| character_sets_dir       | /usr/share/mysql/charsets/ |
+--------------------------+----------------------------+
8 rows in set (0.00 sec)
</code>

回复内容：

先上代码：

<code>php</code><code class="lang-php"><form method="post" action="<?php%20echo%20htmlspecialchars(%24_SERVER%5B" php_self>"> 
<input name="qname" type="text" class="textlable" id="lname" onfocus="if (value =='姓名'){value ='';}" onblur="if (value == ''){value='姓名';}" value="姓名">
<input name="qcont" type="submit" value="查询">
</form>
<?php if ($_SERVER["REQUEST_METHOD"] == "POST") {
     if ($_POST["qname"] =="姓名") {
     $nameErr = "请输入姓名";
     }else {
        $con = mysql_connect("localhost","root","123456");
if (!$con)
  {
  die('Could not connect: ' . mysql_error());
  }
    mysql_query("set names ’utf8’ ");  
    mysql_query("set character_set_client=utf8");  
    mysql_query("set character_set_results=utf8"); 
    mysql_select_db("gkweb", $con);
    $sql="select c_name,c_extension,c_mail from gk_contacts where c_name='".$_POST["qname"]."'";
    echo $sql;
    $result = mysql_query($sql);
    echo "<table align='center' class='altrowstable' id='alternatecolor'><tr>
<th>姓名</th>
<th>座机</th>
<th>电子邮件</th>
</tr>";
    echo 123;
while($row = mysql_fetch_array($result))
  {
  echo "<tr>";
  echo "<td>" . $row['c_name'] . "</td>";
  echo "<td>" . $row['c_extension'] . "</td>";
  echo "<td>" . $row['c_mail'] . "</td>";
  echo "</tr>";
  }
echo "";
mysql_close($con);
     }}
?>
</code>

不知道为什么只要使用了带where的sql进行查询就没有输出结果。
但是使用$sql="select c_name,c_extension,c_mail from gk_contacts"却能输出所有数据.
我也使用echo $sql;输出的SQL在数据库后台查询了，能输出结果。求大神告知是哪里写错了。
不知道怎么排版，求不嫌弃。谢谢
刚才有大神说可能是数据库字符编码的问题，可我数据库都是用的UTF8

<code>bash</code><code class="lang-bash">MariaDB [(none)]>  show variables like '%char%';
+--------------------------+----------------------------+
| Variable_name            | Value                      |
+--------------------------+----------------------------+
| character_set_client     | utf8                       |
| character_set_connection | utf8                       |
| character_set_database   | utf8                       |
| character_set_filesystem | binary                     |
| character_set_results    | utf8                       |
| character_set_server     | utf8                       |
| character_set_system     | utf8                       |
| character_sets_dir       | /usr/share/mysql/charsets/ |
+--------------------------+----------------------------+
8 rows in set (0.00 sec)
</code>

mysql_query("set names ’utf8’ "); 改成mysql_query("set names utf8 ")

先确认一下记录是否存在或者qname是否拼写错误。如果都无误的话。那应该就是数据库表的编码问题了。