Input field containing double quotes value
Use htmlentities:
<input value="<?php echo htmlentities($value);?>">
I suppose your "text box" is an HTML <input> element?
If so, you are displaying it using something like this:
echo '<input name="..." value="' . $yourValue . '" />';
If it's the case, you need to escape the HTML that's contained in your variable, with htmlspecialchars:
echo '<input name="..." value="' . htmlspecialchars($yourValue) . '" />';
Note that you might have to add a couple of parameters, especially to specify the encoding your are using.
This way, considering $yourValue has been initialized like this :
$yourValue = '5 " inches';
You'll get from this generated HTML:
<input name="..." value="5 " inches" />
To that one, which works much better:
<input name="..." value="5 " inches" />