what is the difference between print_r() and echo? are they the same ?

echo and print_r are 2 different beasts. echo is a language construct that can "act" as a function, and by act, I mean you can echo 1 string if its within parenthesis. These are valid.

echo ("Hello");
echo "Hello", "world";

However, this is not:

echo ("hello", "world");

echo, i believe, will only output data types of string, int, bool, float. It will not output arrays, or objects. If you try to echo an array, it will output Array with no details to it.

print_r is a function that will format the variable that you pass into it. So for instance, if you have an array, it will format it to a human readable output.

$var = array(1,2,3,4);
print_r($var);

// Outputs:
Array
(
    [0] => 1
    [1] => 2
    [2] => 3
    [3] => 4
)

But you can also store the results of print_r into a variable with a second param to print_r, which will prevent any output from the function.

$var = array(1,2,3,4);
$output = print_r($var, true);

echo $output; // outputs the returned string from print_r

var_dump is another function that goes into slightly more detail that print_r, where it will output the the data type and values of what you're passing into it

$var = array(1,2,3,4);
var_dump($var);
// Outputs:
array(4) {
  [0]=>
  int(1)
  [1]=>
  int(2)
  [2]=>
  int(3)
  [3]=>
  int(4)
}

$string = "Hello World!";
var_dump($string);

// Outputs:
string(12) "Hello World!"

I hope this helps clarify the similarities and differences between echo, print_r, and var_dump.