PHP built-in functions

<?php
namespace Codecademy;

//Built-in functions

//reverse string
echo strrev(".pu ti peeK .taerg gniod er'uoY");

//to lower case
echo strtolower("SOON, tHiS WILL Look NoRmAL.");

//repeat string for certain no. of times
echo str_repeat("\nThere's no place like home.\n", 3);


$essay_one = "I really enjoyed the book. I thought the characters were really interesting. The plot of the novel was really engaging. I really felt the characters' emotions. They were really well-written. I really wish the ending had been different though.";

$essay_two = "Obviously this is a really good book. You obviously would not have made us read it if it wasn't. I felt like the ending was too obvious though. It was so obvious who did it right away. I think the thing with the light was obviously a metaphor for life. It would have been better if the characters were less obvious about their secrets.";

// count the no. of times the substring in 2nd parameter appears in the string (1st parameter)
echo substr_count($essay_one, "really");

echo substr_count($essay_two, "obvious"); //this includes "obviously" because the function is not concerned with which characters come before or after the string

// using absolute value function
function calculateDistance($first, $second){
  return abs($first - $second);
}

//using round function
function calculateTip($meal){
  return round($meal*1.18);
}

echo calculateDistance(-1,99);
echo calculateTip(100);

// Random numbers generator
echo getrandmax();  //to get the largest possible random integer
echo "\n";
echo rand();        // get number between 0 and the max above
echo "\n";
echo rand(1,52);    // get number within the range (1 and 52 inclusive)

// using str_pad() to understand PHP documentation
$a = 29;
$b = "You did it!";
$c = STR_PAD_BOTH;
$d = "*~*";

echo str_pad($b, $a, $d, $c);

// using other built-in functions
function convertToShout($say){
  return strtoupper($say) . "!";
}

function tipGenerously($meal){
  return ceil($meal*1.2);
}