Chapter 2. Operators

While Chapter 1 introduced the foundational building blocks of PHP—variables to store arbitrary values—these building blocks are useless without some kind of glue to hold them together. This glue is the set of operators established by PHP. Operators are the way you tell PHP what to do with certain values—specifically how to change one or more values into a new, discrete value.

In almost every case, an operator in PHP is represented by a single character or by repeated uses of that same character. In a handful of cases, operators can also be represented by literal English words, which helps disambiguate what the operator is trying to accomplish.

This book does not attempt to cover every operator leveraged by PHP; for exhaustive explanations of each, refer to the PHP Manual itself. Instead, the following few sections cover some of the most important logical, bitwise, and comparison operators before diving into more concrete problems, solutions, and examples.

Logical Operators

Logical operations are the components of PHP that create truth tables and define basic and/or/not grouping criteria. Table 2-1 enumerates all of the character-based logical operators supported by PHP.

Table 2-1. Logical operators

Expression	Operator name	Result	Example
$x && $y	and	true if both $x and $y are true	true && true == true
$x || $y	or	true if either $x or $y is true	true || false == true
!$x	not	true if $x is false (and vice versa)	!true == false

The logical operators ...