生成UUID

/**

 * 生成UUID

 * */

function create_guid(){

    $microTime = microtime();

    list($a_dec, $a_sec) = explode(" ", $microTime);

    $dec_hex = dechex($a_dec* 1000000);

    $sec_hex = dechex($a_sec);

    ensure_length($dec_hex, 5);

    ensure_length($sec_hex, 6);

    $guid = "";

    $guid .= $dec_hex;

    $guid .= create_guid_section(3);

    $guid .= '-';

    $guid .= create_guid_section(4);

    $guid .= '-';

    $guid .= create_guid_section(4);

    $guid .= '-';

    $guid .= create_guid_section(4);

    $guid .= '-';

    $guid .= $sec_hex;

    $guid .= create_guid_section(6);

    return $guid;

}

function ensure_length(&$string, $length){

    $strlen = strlen($string);

    if($strlen < $length){

         $string = str_pad($string,$length,"0");

    }else if($strlen > $length){

         $string = substr($string, 0, $length);

    }

}

function create_guid_section($characters){

    $return = "";

    for($i=0; $i<$characters; $i++){

         $return .= dechex(mt_rand(0,15));

    }

    return $return;

}

经过测试，这个还不错！