元素宽度％基于PHP变量值

Consider the following:

$a=25;
$b=75;

I would like to show a percentage bar based on value of $a and $b. I would like to express the percentage bar as a div.

I guess I would need to do the following:

<div id='container'>
  <div id='a'></div>
    <div id='b'></div>
</div>

#container{
width: 100%
}

#a{
Width: $a //here I need to get the value of $a
}

Any Idea how I can implement this?

I need to get this in an external stylesheet.

What I hope to achieve, keep in mind that value of $a and $b varies

You can only use PHP variables in CSS files when you build (and save) them dynamically. If the value changes often (when it depends on the page or the content for example), I would not recommend that. Instead you can perfectly use inline style blocks:

<style> #a { width: <php echo $a; ?>; } </style>

Edit: added an example as requested in the comments:

To make sure all elements have 100% of their container's width, just substract $t1 from 100:

<?php
    $width_t1 = 25;
    $style_t1 = 'float: left; width: ' . $width_t1 . '%; height:50px;';
    $width_t2 = 100 - $width_t1;
    $style_t2 = 'float: left; width: ' . $width_t2 . '%;';

    if ($count > 0) {
        $style_t1 .= ' background-color: red';
    } else {
        $style_t1 .= ' background-color: blue';
    }
?>
<div id="t1" style="<?php echo $style_t1; ?>">...</div>
<div id="t2" style="<?php echo $style_t2; ?>">...</div>