$var = "10";
$value = 10 + $var;
var_dump($value); // int(20)

$var = "10";
$value = 10 + $var;
$value = (string)$value;
var_dump($value); // string(2) "20"

$var = "10";
$value = (int)$var;
$value = $value . ' TaDa!';
var_dump($value); // string(8) "10 TaDa!"

// example 1
$foo = 0;
$foo = (string)$foo;
$foo = '# of Reasons for the programmer to type cast $foo as a string: ' . $foo;

// example 2
$foo = 0;
$foo = (int)$foo;
$foo = '# of Reasons for the programmer to type cast $foo as a string: ' . $foo;

Menu Item 1 .............. $ 4
Menu Item 2 .............. $ 7.5
Menu Item 3 .............. $ 3

$price = '7.50'; // a string from the database layer.
echo 'Menu Item 2 .............. $ ' . (float)$price;

var a = 5;
var b = "10"
var incorrect = a + b; // "510"
var correct = a + Number(b); // 15

console.log("5" > "10" ? "true" : "false"); // true

echo "5" > "10" ? "true" : "false";  // false!

function testprint(string $a) {
    echo $a;
}

$test = 5;
testprint((string)5); // "Catchable fatal error: Argument 1 passed to testprint()
                      //  must be an instance of string, string given" WTF?

console.log("0" ? "true" : "false"); // True, as expected. Non-empty string.

echo "0" ? "true" : "false"; // False! This one probably causes a lot of bugs.

$val = "test";
$val2 = "10";
$intval = (int)$val; // 0
$intval2 = (int)$val2; // 10
$boolval = (bool)$intval // false
$boolval2 = (bool)$intval2 // true
$props = (array)$myobject // associative array of $myobject's properties

function get_by_id ($id) {
   $id = (int)$id;
   $q = "SELECT * FROM table WHERE id=$id LIMIT 1";
   ........
}

$amount = (float) $_POST['amount'];

if( $amount > 0 ){
    // Do some maths
}

$tags = _GET['tags'];
foreach ($tags as $tag) {
    echo 'tag: ', $tag;
}

$tags = (array) _GET['tags'];
foreach ($tags as $tag) {
    echo 'tag: ', $tag;
}

{ "user" : { "id" : "1", "name" : "Bob" } }

{ "user" : { "id" : 1, "name" : "Bob" } }