Integers can be specified in decimal (base 10), hexadecimal (base 16) and octal (base 8), and binary (base 2) notation, optionally preceded by a sign (- or +).
To explicitly convert a value to integer, use either the (int) or (integer) casts and this is case-insensitive.
<?php
$octal = 010; // 8 - base 8
$decimal = 10; // 10 - base 10
$hexadecimal = 0x10; // 16 - base 16
$binary = 0b10; // 2 - base 2
$str_test = "10"; // string "10"
$int_test = (int)$str_test; // convert string to integer
?>