In PHP, TRUE represents the
value 1 and FALSE represents 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 if, switch, and the ? operator.
To skip the current iteration of a loop and move on to the next
one, use a continue
statement.
Loops using for statements
are more powerful than while loops
because they support two additional parameters to control the loop
handling.
Most conditional expressions in if and 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 string. A NULL value is evaluated as false and
therefore does not trigger execution.