function isosceles($line,$sing){
  $tab ='=';  
  for($i=1;$i < $line+1;$i++){
    $blank = print_blank($i,$line,$tab);
    $code = print_code($i,$sing);
    echo $blank.$code.$blank."<br>";
  }
}
function print_blank($num,$line,$tab){
  $blank ='';
  for($i=$num;$i<$line;$i++){
    $blank.=$tab;
  }
  return $blank;
}
function print_code($num,$sing){
  $code ='';
  for($i=0;$i<(2*($num-1)+1);$i++){
    $code.=$sing;
  }
  return $code;
}
$line = 5;
$sing = "*";
isosceles($line,$sing);