test.less

@import "variables.less";
.navbarVerticalAlign(@elementHeight) {
  margin-top: (@navbarHeight - @elementHeight) / 2;
}
.border-radius(@radius) {
  -webkit-border-radius: @radius;
     -moz-border-radius: @radius;
          border-radius: @radius;
}

// Single Corner Border Radius
.border-top-left-radius(@radius) {
  -webkit-border-top-left-radius: @radius;
      -moz-border-radius-topleft: @radius;
          border-top-left-radius: @radius;
}
.border-top-right-radius(@radius) {
  -webkit-border-top-right-radius: @radius;
      -moz-border-radius-topright: @radius;
          border-top-right-radius: @radius;
}
.border-bottom-right-radius(@radius) {
  -webkit-border-bottom-right-radius: @radius;
      -moz-border-radius-bottomright: @radius;
          border-bottom-right-radius: @radius;
}
.border-bottom-left-radius(@radius) {
  -webkit-border-bottom-left-radius: @radius;
      -moz-border-radius-bottomleft: @radius;
          border-bottom-left-radius: @radius;
}

#font {
  #family {
    .serif() {
      font-family: @serifFontFamily;
    }
    .sans-serif() {
      font-family: @sansFontFamily;
    }
    .monospace() {
      font-family: @monoFontFamily;
    }
  }
  .shorthand(@size: @baseFontSize, @weight: normal, @lineHeight: @baseLineHeight) {
    font-size: @size;
    font-weight: @weight;
    line-height: @lineHeight;
  }
}
#font {
  .serif(@size: @baseFontSize, @weight: normal, @lineHeight: @baseLineHeight) {
    #font > #family > .serif;
    #font > .shorthand(@size, @weight, @lineHeight);
  }
  .sans-serif(@size: @baseFontSize, @weight: normal, @lineHeight: @baseLineHeight) {
    #font > #family > .sans-serif;
    #font > .shorthand(@size, @weight, @lineHeight);
  }
  .monospace(@size: @baseFontSize, @weight: normal, @lineHeight: @baseLineHeight) {
    #font > #family > .monospace;
    #font > .shorthand(@size, @weight, @lineHeight);
  }
}

.navbar-search {
  position: relative;
  float: left;
  .navbarVerticalAlign(30px); // Vertically center in navbar
  margin-bottom: 0;
  .search-query {
    margin-bottom: 0;
    padding: 4px 14px;
    #font > .sans-serif(13px, normal, 1);
    .border-radius(15px); // redeclare because of specificity of the type attribute
  }
}

test.php

<?php

require_once('lessc.inc.php');

$compiler = new lessc();
$output = $compiler->compileFile('/Users/nicols/git/ext/lessphp/test.less');

file_put_contents('after.css', $output);