php为字符串前后添加指定数量字符的方法

function str_prefix($str, $n=1, $char=" "){
  for ($x=0;$x<$n;$x++){$str = $char.$str;}
  return $str;
}
function str_suffix($str, $n=1, $char=" "){
  for ($x=0;$x<$n;$x++){$str = $str.$char;}
  return $str;
}

str_prefix('test',3,'-')=>returns'---test'
str_suffix('test',3,'-')=> returns 'test---'