all / commands use a space between their arguments (theres no way to change this that I know of).
so try the following:
function servercmdui(%client, %text1, %text2, %text3, %text4)
{
messageAll('', "<color:FFFFFF>"@ %client.getPlayerName() SPC %text1 SPC %text2 SPC %text3 SPC %text4);
}