DRY Picture element media queries

dry-picture-element-media-queries

<?php
    // Define picture element media query values here
    $m_mqs  = 'min-width:321px';
    $l_mqs  = 'min-width:641px';
    $xl_mqs = 'min-width:1281px';
?>

<picture alt="Alt tag describing the image represented"> 
    <source src="photo-s.jpg"/> 
    <source src="photo-m.jpg" media="<?php ehco $m_mqs; ?>"/> 
    <source src="photo-l.jpg" media="<?php ehco $l_mqs; ?>"/> 
    <source src="photo-xl.jpg" media="<?php ehco $xl_mqs; ?>" /> 
    <img src="photo-s.jpg" /> 
</picture>