php-regex-meta-description.php

<?php

    /**
     * Attempts to parse given meta tag's content from given html;
     * deals with 'standard' and Open Graph meta tags.
     * 
     * Order of meta tag attributes could be swapped around e.g. can either be
     * name="..." content="..."
     * or
     * content="..." name="..." 
     * 
     * so we try to get meta tag content in 'swapped' way
     * if we don't get in 'straight'
     * 
     * @param string $html
     * - html, which contains meta tags
     * @param string $tagName
     * - name of meta tag, e.g. 'description'
     * @return null
     */
    function getMetaTag($html, $tagName) {
        $matches = array();

        preg_match('/<meta.*?(name|property)=("|\')(og:)?' . $tagName . '("|\').*?content=("|\')(.*?)("|\')/i', $html, $matches);
        if(isset($matches[6])) {
            return trim($matches[6]);
        }

        preg_match('/<meta.*?content=("|\')(.*?)("|\').*?(name|property)=("|\')(og:)?' . $tagName . '("|\')/i', $html, $matches);
        if(isset($matches[2])) {
                return trim($matches[2]);
        }

        return null;
    }