Send a private message to an IRC bot

I have a php script to join a channel on this IRC server: irc.worldnet.net Thanks to the server response I can say that I joined the channel successfully, and that the bot is in the users list. However, this command:

MSG bot_nickname hello my friend !

issues an 'msg: unknown command' response. An when I send this line:

PRIVMSG bot_nickname : hello my friend !

There is no response from the bot (I don't have any error message anyway). Is there something wrong with the commands I send ?

Here is the php code that I use:

<?php

$channel_sent = false;
$channel_joined = false;
$msg_sent = false;
set_time_limit(0);
ini_set('display_errors', 'on');

$config = array(
    'server' => 'irc.worldnet.net',
    'port' => 6667,
    'nick' => 'cesame'.rand(),
    'channel' => '#nc-irc-challs'
);

$server = array();
$server['SOCKET'] = @fsockopen($config['server'], $config['port'], $errno, $errstr, 2); 

if($server['SOCKET'])
{
    SendCommand("PASS NOPASS\n\r");
    SendCommand("NICK " . $config['nick'] . "\n\r"); 
    SendCommand("USER " . $config['nick'] . " USING PHP IRC\n\r");    
    SendCommand("JOIN " . $config['channel'] . "\n\r");

    while(!feof($server['SOCKET'])) {
            ReadServer();
            flush();
            sleep(1);
    }
}

function ReadServer(){
    global $server;
    global $config;
    global $channel_joined;
    global $channel_sent;
    global $msg_sent;
    $server['READ_BUFFER'] = fgets($server['SOCKET'], 1024);
    echo "[RECEIVE] ".$server['READ_BUFFER']."<br>\n\r";  

    if(substr($server['READ_BUFFER'], 0, 6) == "PING :") { 
        SendCommand("PONG :".substr($server['READ_BUFFER'], 6)."\n\r"); 
    }
    if(strpos($server['READ_BUFFER'], "#nc-irc-challs :End of /NAMES list")){
        $channel_joined = true;
    }
    if(trim($server['READ_BUFFER']) == "" && $channel_joined &&!$msg_sent) {
        SendCommand('PRIVMSG Daneel : .challenge_caesar start' . "\n\r");
        $msg_sent = true;
    }
}

function SendCommand ($cmd)
{
    global $server; //Extends our $server array to this function
    @fwrite($server['SOCKET'], $cmd, strlen($cmd)); //sends the command to the server
    echo "[SEND] $cmd <br>"; //displays it on the screen
} 

?>

So I followed you advices. This is the logs that I Get:

[RECEIVE] :cesame1582!~cesame158@Wnet-59540.41.55.213.rev.sfr.net JOIN :#nc-irc-challs 
[RECEIVE] :Vidar.IRC.Worldnet.Net 332 cesame1582 #nc-irc-challs :NewbieContest -- http://www.newbiecontest.org/ (channel officiel : #newbiecontest) -- Rappel : aucune Ã©preuve ne peut se rÃ©soudre en bruteforce. 
[RECEIVE] :Vidar.IRC.Worldnet.Net 333 cesame1582 #nc-irc-challs zours 1195848644 
[RECEIVE] :Vidar.IRC.Worldnet.Net 353 cesame1582 = #nc-irc-challs :cesame1582 \o_ @Eole +Daneel 
[RECEIVE] :Vidar.IRC.Worldnet.Net 366 cesame1582 #nc-irc-challs :End of /NAMES list. 
[SEND] PRIVMSG Daneel : .challenge_caesar start 
[RECEIVE] :Global!Services@Worldnet.Net NOTICE cesame1582 :[Logon News - Apr 07 2004] Use irc.worldnet.net to join our network, thanks | Dorenavant, utilisez irc.worldnet.net pour joindre notre reseau, merci. 
[RECEIVE] :Global!Services@Worldnet.Net NOTICE cesame1582 :[Logon News - Jan 07 2007] If you see a connection on port 23, 1080, 3128 or 8080 from 194.117.194.78 this is NOT an attack! It's our insecure proxy detector. 
[RECEIVE] :Global!Services@Worldnet.Net NOTICE cesame1582 :[Logon News - Feb 07 2007] Vous pouvez utiliser le port 7000 pour une connexion en SSL. You can use port 7000 with a secure SSL connection. 
[RECEIVE] :Global!Services@Worldnet.Net NOTICE cesame1582 :[Logon News - Oct 14 2009] Salons officiels du reseau Worldnet : #worldnet - #help pour de l'aide sur IRC et l'informatique en general. - ##opers pour les problemes réseau spécifiques à Worldnet. 
[RECEIVE] :Global!Services@Worldnet.Net NOTICE cesame1582 :[Random News - Apr 24 2004] Pour avoir de l'aide sur les commandes des services, visitez http://help.irc.worldnet.net 
[RECEIVE] :NickServ!Services@Worldnet.Net NOTICE cesame1582 :Your nick isn't registered. 
[RECEIVE] 
[RECEIVE] PING :Vidar.IRC.Worldnet.Net 
[SEND] PONG :Vidar.IRC.Worldnet.Net 
[RECEIVE] 
[RECEIVE] PING :Vidar.IRC.Worldnet.Net 
[SEND] PONG :Vidar.IRC.Worldnet.Net

The IRC server generally does not send empty strings.

If you want a command to be issued once the BOT is in the channel, you should be sending it as soon as you know it's in the channel, which is at the end of the /NAMES list, or once you receive the TOPIC.

Also, the syntax for PRIVMSG is as follows: