//PWN
public onSocketReceiveData(Socket:id, remote_clientid, data[], data_len) {

    if(data[0] == '1') { // IsPlayerConnected

  		new pName[MAX_PLAYER_NAME], isConnected[10];
  		format(isConnected, sizeof isConnected, "Offline");

    	for(new i = 0, j = GetPlayerPoolSize(); i <= j; i++) {

    		print("Called");
    		if(!IsPlayerConnected(i)) continue;

    		GetPlayerName(i, pName, sizeof pName);
    		if(!strcmp(pName, data[2], false)) {

    			format(isConnected, sizeof isConnected, "Online");
    			break;
    		}
    	}
    	socket_sendto_remote_client(id, remote_clientid, isConnected);
    }
    printf("Remote client [%d] has sent: %s", remote_clientid, data); // id & data
    return 1;
}

//The way I call the PHP script below
function BuyVehicle(price, id)
{
    $.ajax({
        type: 'POST',
        url: 'buy_action.php',
        data: 'vehicleModel=' + id + '&vehiclePrice=' + price,
        success: function(response) {

            if(response == '1') {

                playerDisconnected();
            }
        }
    });
}

//PHP
<?php
    session_start();

    set_time_limit(0);
    ob_implicit_flush();

    $address = '127.0.0.1';
    $port = 7778;

    $socket = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
    socket_connect($socket, $address, $port);

    $st = "1|".$_SESSION["sessionUsername"]."";
    socket_write($socket, $st, strlen($st));

    $buffer = "";
    socket_recv($socket, $buffer, 2048, MSG_WAITALL);

    if(strcmp($buffer, "Online") != 0) {

        echo '1';
    }
    socket_close($socket);
?>