Disable the fields and then enable them before the form is submitted:

jQuery code:

jQuery(function ($) {        
  $('form').bind('submit', function () {
    $(this).find(':input').prop('disabled', false);
  });
});

I`ve been looking for a solution for this, and since i didnt find a solution in this thread i did my own.

// With jQuery
$('#selectbox').focus(function(e) {
    $(this).blur();
});

Simple, you just blur the field when you focus on it, something like disabling it, but you actually send its data.

I faced a slightly different scenario, in which I only wanted to not allow the user to change the selected value based on an earlier selectbox. What I ended up doing was just disabling all the other non-selected options in the selectbox using

$('#toSelect').find(':not(:selected)').prop('disabled',true);

it dows not work with the :input selector for select fields, use this:

    jQuery(function() {

    jQuery('form').bind('submit', function() {
        jQuery(this).find(':disabled').removeAttr('disabled');
    });

    });

The easiest way i found was to create a tiny javascript function tied to your form :

function enablePath() {
    document.getElementById('select_name').disabled= "";
}

and you call it in your form here :

<form action="act.php" method="POST" name="form_name" onSubmit="enablePath();">

Or you can call it in the function you use to check your form :)

Same solution suggested by Tres without using jQuery

<form onsubmit="document.getElementById('mysel').disabled = false;" action="..." method="GET">

   <select id="mysel" disabled="disabled">....</select>

   <input name="submit" id="submit" type="submit" value="SEND FORM">
</form>

This might help someone understand more, but obviously is less flexible than the jQuery one.

I use next code for disable options in selections

<select class="sel big" id="form_code" name="code" readonly="readonly">
   <option value="user_played_game" selected="true">1 Game</option>
   <option value="coins" disabled="">2 Object</option>
   <option value="event" disabled="">3 Object</option>
   <option value="level" disabled="">4 Object</option>
   <option value="game" disabled="">5 Object</option>
</select>

// Disable selection for options
$('select option:not(:selected)').each(function(){
 $(this).attr('disabled', 'disabled');
});

Just add a line before submit.

$("#XYZ").removeAttr("disabled");

Or use some JavaScript to change the name of the select and set it to disabled. This way the select is still submitted, but using a name you aren't checking.

I whipped up a quick (Jquery only) plugin, that saves the value in a data field while an input is disabled. This just means as long as the field is being disabled programmaticly through jquery using .prop() or .attr()... then accessing the value by .val(), .serialize() or .serializeArra() will always return the value even if disabled :)

Shameless plug: https://github.com/Jezternz/jq-disabled-inputs

Based on the solution of the Jordan, I created a function that automatically creates a hidden input with the same name and same value of the select you want to become invalid. The first parameter can be an id or a jquery element; the second is a Boolean optional parameter where "true" disables and "false" enables the input. If omitted, the second parameter switches the select between "enabled" and "disabled".

function changeSelectUserManipulation(obj, disable){
    var $obj = ( typeof obj === 'string' )? $('#'+obj) : obj;
    disable = disable? !!disable : !$obj.is(':disabled');

    if(disable){
        $obj.prop('disabled', true)
            .after("<input type='hidden' id='select_user_manipulation_hidden_"+$obj.attr('id')+"' name='"+$obj.attr('name')+"' value='"+$obj.val()+"'>");
    }else{
        $obj.prop('disabled', false)
            .next("#select_user_manipulation_hidden_"+$obj.attr('id')).remove();
    }
}

changeSelectUserManipulation("select_id");

I found a workable solution: remove all the elements except the selected one. You can then change the style to something that looks disabled as well. Using jQuery:

jQuery(function($) {
    $('form').submit(function(){
        $('select option:not(:selected)', this).remove();
    });
});

<select id="example">
    <option value="">please select</option>
    <option value="0" >one</option>
    <option value="1">two</option>
</select>



if (condition){
    //you can't select
    $("#example").find("option").css("display","none");
}else{
   //you can select
   $("#example").find("option").css("display","block");
}

Another option is to use the readonly attribute.

<select readonly="readonly">
    ....
</select>

With readonly the value is still submitted, the input field is grayed out and the user cannot edit it.

Edit:

Quoted from http://www.w3.org/TR/html401/interact/forms.html#adef-readonly:

• Read-only elements receive focus but cannot be modified by the user.
• Read-only elements are included in tabbing navigation.
• Read-only elements may be successful.

When it says the element may be succesful, it means it may be submitted, as stated here: http://www.w3.org/TR/html401/interact/forms.html#successful-controls