To pass more than one css rule, but also a class, an id, or any html attribute to highlighted element, we can escape a quote to close the inline styling:    ini_set('highlight.string', '#F8F8F8 ; font-size:1.4em\" class=\'string\' ');

*** Additions to the previous message ***To change the style directly from a CSS file, it is recommended to only go through classes instead of hard-coding it.<?php    // Create an array with default php functions    $functions = array("default", "html", "keyword", "string", "comment");    // Replace color code (ex: #FF8000) with class name (ex:"highlight-comment")    foreach ($functions as $value) {        ini_set("highlight.$value", "highlight-$value;");    }    $content = highlight_file($filename, true);    // or    $content = highlight_string($string, true);    // Convert style="color: highlight-function" into class="highlight-function" into $content    // It allows you to modify only the default functions    foreach ($functions as $value) {        $content = preg_replace("/style=\"color: highlight-$value;\"/", "class=\"highlight-$value\"", $content);    }?>And in the CSS file (for example) :.highlight-html { color: #000000; }.highlight-default { color: #0000bb; }.highlight-keyword { color: #007700; font-weight: bold; }.highlight-string { color: #dd0000; }.highlight-comment { color: #ff8000; }

To change the style directly from a CSS file, it is recommended to only go through classes instead of hard-coding it.<?php    $functions = array("default", "html", "keyword", "string", "comment");    foreach ($functions as $value) {        ini_set("highlight.$value", "highlight-$value;");    }?>And in the CSS file (for example) :.highlight-html { color: #000000; }.highlight-default { color: #0000bb; }.highlight-keyword { color: #007700; font-weight: bold; }.highlight-string { color: #dd0000; }.highlight-comment { color: #ff8000; }