string questions inbuild functions

$x = 'a a Hello World!';
$y = "Hello";
echo strlen($y); echo '<br>';// length of Hello is output 5
echo strpos($x,$y); echo '<br>';// output 4 ie., a a H===starts at 4 position
echo str_replace("Hello", "nice", $x); // replacing word in sentence


output
5
4
a a nice World!


$a = array("a", "b", "c", "d", "e");
 array_pop($a);
echo "ABCDE=ABCD "; print_r(($a)); 
//print_r('array(a b c d e) pop value='.$b);
echo '<br>';
$c = array_slice($a, 2);

echo "ABCDE=CD ";print_r($c);

ABCDE=ABCD Array ( [0] => a [1] => b [2] => c [3] => d ) 
ABCDE=CD Array ( [0] => c [1] => d )