URL安全的Base64编码（用'-'代替'+'，用'_'代替'/'，去掉末尾的padding），PHP实现

url_base64.php

<?php

// public url_base64_encode(bin) {{{ 
/**
 * url_base64_encode 生成URL安全的Base64编码
 * 
 * @param string $bin 
 * @access public
 * @return string
 */
function url_base64_encode($bin) {
    $base64 = base64_encode($bin);
    $base64 = str_replace('+', '-', $base64);
    $base64 = str_replace('/', '_', $base64);
    $base64 = str_replace('=', '', $base64);
    return $base64;
}
// }}}

// public url_base64_decode(base64) {{{ 
/**
 * url_base64_decode 解码URL安全的Base64
 * 
 * @param mixed $base64 
 * @access public
 * @return void
 */
function url_base64_decode($base64) {
    $base64 = str_replace('-', '+', $base64);
    $base64 = str_replace('_', '/', $base64);
    /* 
     * Put the padding back (a little tricky)
     * Base64 has one or two '=' at the end as padding.
     * 3 bytes == 4 Base64 chars
     * 1 byte left: two B64 chars and two '='
     * 2 bytes left: three B64 chars and one '='
     */
    $len = strlen($base64);
    if ($len % 4 == 2) $base64 .= '==';
    elseif ($len % 4 == 3) $base64 .= '=';
    return base64_decode($base64);
}
// }}}

?>