Expressions and Operators
An expression is a bit of PHP that can be evaluated to produce a value. The simplest expressions are literal values and variables. A literal value evaluates to itself, while a variable evaluates to the value stored in the variable. More complex expressions can be formed using simple expressions and operators .
An operator takes some values (the operands)
and does something (for instance, adds them together). Operators are
written as punctuation symbols—for instance, the
+ and - familiar to us from math. Some
operators modify their operands, while most do not.
Table 2-3 summarizes the operators in PHP, many of which were borrowed from C and Perl. The column labeled “P” gives the operator’s precedence; the operators are listed in precedence order, from highest to lowest. The column labeled “A” gives the operator’s associativity, which can be L (left-to-right), R (right-to-left), or N (non-associative).
Create new object
Bitwise shift left
Bitwise shift right
Less than, less than or equal
Greater than, greater than or equal
Type and value equality
Type and value inequality