Primitives

Booleans

• To specify a boolean literal, use either the keyword TRUE or FALSE. Both are case-insensitive.
• Avoid comparing a boolean to a nonboolean, as the result will often be different than expected - non-intutive; it converts the nonboolean to a boolean, and then compares the two boolean values.

Examples

<?php 
$mybool = true;
if ($mybool) {
    echo "text\n";
}
?>

Integers

• Hexadecimal values are preceded by 0x or 0X.
• Octal values are preceded by 0 (zero).

• PHP does not support unsigned integers.
• At present, integers are usually 32-bits (platform dependent).
• A value outside of the range of an integer will be treated as a float.
• Division of two integers yields a float value.

Floating point numbers

12.34
.34
12. 
1.2e3
7E-10

• aka "floats", "doubles", "real numbers"
• Never compare two float values (due to possible loss of precision).