the value 1 and
NULL, which can be
thought of as “nothing” and is output as the empty string.
The simplest forms of expressions are literals (such as numbers and strings) and variables, which simply evaluate to themselves.
The difference between unary, binary and ternary operators is the number of operands each requires (one, two, and three, respectively).
The best way to force your own operator precedence is to place parentheses around subexpressions to which you wish to give high precedence.
Operator associativity refers to the direction of processing (left-to-right or right-to-left).
You use the identity operator when you wish to bypass PHP’s automatic operand type changing (also called type casting).
The three conditional statement types are
switch, and the
To skip the current iteration of a loop and move on to the
next one, use a
statements are more powerful than
while loops, because they support two
additional parameters to control the loop handling.
Most conditional expressions in
while statements are literal (or
Boolean) and therefore trigger execution when they evaluate to
TRUE. Numeric expressions
trigger execution when they evaluate to a nonzero value. String
expressions trigger execution when they evaluate to a nonempty
NULL value is ...