【PHP】CI框架原始碼分析核心檔案之Utf8.php

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defined('BASEPATH') OR exit('No direct script access allowed');

/**
 * Utf8 Class
 *
 * Provides support for UTF-8 environments
 *
 * @package        CodeIgniter
 * @subpackage    Libraries
 * @category    UTF-8
 * @author        EllisLab Dev Team
 * @link        /user_guide/libraries/utf8.html
 */
class CI_Utf8 {

    /**
     * Class constructor
     *
     * Determines if UTF-8 support is to be enabled.
     *
     * @return    void
     */
    public function __construct()
    {
        if (
            defined('PREG_BAD_UTF8_ERROR')                // PCRE must support UTF-8--perl正規表示式需要支援UTF-8
            && (ICONV_ENABLED === TRUE OR MB_ENABLED === TRUE)    // iconv or mbstring must be installed--需要其中任何一個擴充套件的支援(mbstirng or iconv)
            && strtoupper(config_item('charset')) === 'UTF-8'    // Application charset must be UTF-8--配置檔案為UTF-8
            )
        {
            define('UTF8_ENABLED', TRUE);
            log_message('debug', 'UTF-8 Support Enabled');
        }
        else
        {
            define('UTF8_ENABLED', FALSE);
            //寫入日誌
            log_message('debug', 'UTF-8 Support Disabled');
        }

        log_message('info', 'Utf8 Class Initialized');
    }

    // --------------------------------------------------------------------

    /**
     * Clean UTF-8 strings
     *過濾一些非UTF-8的字元
     * Ensures strings contain only valid UTF-8 characters.
     *
     * @param    string    $str    String to clean
     * @return    string
     */
    public function clean_string($str)
    
        //非ASCII字元，則啟動轉換（大於255的字元）
        if ($this->is_ascii($str) === FALSE)
        
            //如果採用mbstring
            if (MB_ENABLED)
            {
                $str = mb_convert_encoding($str, 'UTF-8', 'UTF-8');
            }
            //如果iconv
            elseif (ICONV_ENABLED)
            {
                $str = @iconv('UTF-8', 'UTF-8//IGNORE', $str);
            }
        }

        return $str;
    }

    // --------------------------------------------------------------------

    /**
     * Remove ASCII control characters
     *
     * Removes all ASCII control characters except horizontal tabs,
     * line feeds, and carriage returns, as all others can cause
     * problems in XML.
     *刪除ASCII控制字元
     * @param    string    $str    String to clean
     * @return    string
     */
    public function safe_ascii_for_xml($str)
    {
        return remove_invisible_characters($str, FALSE);
    }

    // --------------------------------------------------------------------

    /**
     * Convert to UTF-8
     *
     * Attempts to convert a string to UTF-8.
     *
     * @param    string    $str        Input string
     * @param    string    $encoding    Input encoding
     * @return    string    $str encoded in UTF-8 or FALSE on failure
     */
    public function convert_to_utf8($str, $encoding)
    {
        //優先mbstring，$encoding輸入的編碼，將輸入的編碼轉換成UTF-8
        if (MB_ENABLED)
        {
            return mb_convert_encoding($str, 'UTF-8', $encoding);
        }
        elseif (ICONV_ENABLED)
        {
            return @iconv($encoding, 'UTF-8', $str);
        }

        return FALSE;
    }

    // --------------------------------------------------------------------

    /**
     * Is ASCII?
     *
     * Tests if a string is standard 7-bit ASCII or not.
     *
     * @param    string    $str    String to check
     * @return    bool
     */
    public function is_ascii($str)
    {
        //匹配到ASCII字元，則返回為true，[^\x00-\x7F]匹配為大於255的字元
        return (preg_match('/[^\x00-\x7F]/S', $str) === 0);
    }

}