title: Disable a button when textbox has data in it
body: <p>I see so many people ask to disable a button when a textbox is empty . how about disable a button when a textbox has data ?</p>
  
  <p>this is my button code</p>
  
  <pre><code>&lt;input type="submit" name="submit" value="Reserve" /&gt;
  </code></pre>
  
  <p>this is my textbox code </p>
  
  <pre><code>Name : &lt;br&gt;&lt;br&gt;&lt;input type="text" name="name" value="&lt;?php echo $name;?&gt;"     &lt;?php if($name != "") echo "readonly"?&gt; /&gt; &lt;br&gt;&lt;br&gt;
  
  Name : &lt;br&gt;&lt;br&gt;&lt;input type="text" name="name2" value="&lt;?php echo $name2;?&gt;" &lt;?php if($name2 != "") echo "readonly"?&gt; /&gt; &lt;br&gt;&lt;br&gt;
  </code></pre>