LeftPad in PHP

<?php
function leftPad($inputStr, $paddingLength, $ch = ".") {
    if(strlen($ch) !== 1) {
      return "error";
    }
	
  $paddingLength = $paddingLength - strlen($inputStr);
  $strCh = '';
  for ($i = 0; $i < $paddingLength; ++$i) {
    $strCh = $strCh.$ch;
  }
  
  return $strCh.$inputStr;
}
echo leftPad('1', 1);
echo leftPad('2', 2);
echo leftPad('3', 3);
echo leftPad('4', 4);
echo leftPad('5', 5);
echo leftPad('hello', 7);
echo leftPad("foo",  6);
echo leftPad("foo", 3);
echo leftPad("foobar", 3);
echo leftPad("foo", 6, "?");
?>