PHP automatically converts types when needed (type juggling). You can also cast explicitly.
(int) or intval()(float) or floatval()(string) or strval()(bool) or boolval()(array)false, 0, 0.0, "", "0", [], null evaluate to false.
<?php
// Type juggling (automatic)
var_dump(0 == "foo"); // true (old juggling)
var_dump(0 === "foo"); // false (strict)
// PHP 8: changed behaviour
var_dump(0 == "foo"); // false in PHP 8+
// Explicit casting
$str = "42abc";
$num = (int)$str; // 42
$flt = (float)"3.14px"; // 3.14
// settype
$val = "100";
settype($val, "integer");
var_dump($val); // int(100)
?>