root/trunk/wp-includes/compat.php

<?php
/**
 * WordPress implementation for PHP functions missing from older PHP versions.
 *
 * @package PHP
 * @access private
 */

// Added in PHP 5.0

if (!function_exists('http_build_query')) {
    function http_build_query($data, $prefix=null, $sep=null) {
        return _http_build_query($data, $prefix, $sep);
    }
}

// from php.net (modified by Mark Jaquith to behave like the native PHP5 function)
function _http_build_query($data, $prefix=null, $sep=null, $key='', $urlencode=true) {
    $ret = array();

    foreach ( (array) $data as $k => $v ) {
        if ( $urlencode)
            $k = urlencode($k);
        if ( is_int($k) && $prefix != null )
            $k = $prefix.$k;
        if ( !empty($key) )
            $k = $key . '%5B' . $k . '%5D';
        if ( $v === NULL )
            continue;
        elseif ( $v === FALSE )
            $v = '0';

        if ( is_array($v) || is_object($v) )
            array_push($ret,_http_build_query($v, '', $sep, $k, $urlencode));
        elseif ( $urlencode )
            array_push($ret, $k.'='.urlencode($v));
        else
            array_push($ret, $k.'='.$v);
    }

    if ( NULL === $sep )
        $sep = ini_get('arg_separator.output');

    return implode($sep, $ret);
}

if ( !function_exists('_') ) {
    function _($string) {
        return $string;
    }
}

if (!function_exists('stripos')) {
    function stripos($haystack, $needle, $offset = 0) {
        return strpos(strtolower($haystack), strtolower($needle), $offset);
    }
}

if ( ! function_exists('hash_hmac') ):
function hash_hmac($algo, $data, $key, $raw_output = false) {
    $packs = array('md5' => 'H32', 'sha1' => 'H40');

    if ( !isset($packs[$algo]) )
        return false;

    $pack = $packs[$algo];

    if (strlen($key) > 64)
        $key = pack($pack, $algo($key));
    else if (strlen($key) < 64)
        $key = str_pad($key, 64, chr(0));

    $ipad = (substr($key, 0, 64) ^ str_repeat(chr(0x36), 64));
    $opad = (substr($key, 0, 64) ^ str_repeat(chr(0x5C), 64));

    return $algo($opad . pack($pack, $algo($ipad . $data)));
}
endif;

if ( ! function_exists('mb_strcut') ):
    function mb_strcut( $str, $start, $length=null, $encoding=null ) {
        return _mb_strcut($str, $start, $length, $encoding);
    }
endif;

function _mb_strcut( $str, $start, $length=null, $encoding=null ) {
    // the solution below, works only for utf-8, so in case of a different
    // charset, just use built-in substr
    $charset = get_option( 'blog_charset' );
    if ( !in_array( $charset, array('utf8', 'utf-8', 'UTF8', 'UTF-8') ) ) {
        return is_null( $length )? substr( $str, $start ) : substr( $str, $start, $length);
    }
    // use the regex unicode support to separate the UTF-8 characters into an array
    preg_match_all( '/./us', $str, $match );
    $chars = is_null( $length )? array_slice( $match[0], $start ) : array_slice( $match[0], $start, $length );
    return implode( '', $chars );
}

?>