The tag used to start PHP interpreting code is
<?php ... ?>, which can be shortened
<? ... ?>.
You can use
// for a
single-line comment or
/* ... */ to
span multiple lines.
All PHP statements must end with a semicolon (
With the exception of constants, all PHP variables must begin
A variable holds a value that can be a string, a number, or other data.
$variable = 1 is an
assignment statement, whereas
1 is a comparison operator. Use
$variable = 1 to set the value of
$variable == 1 to find out later in the
1. If you mistakenly use
$variable = 1 where you meant to do a
comparison, it will do two things you probably don’t want: set
1 and return a
true value all the time, no matter what its
previous value was.
A hyphen is reserved for the subtraction operators. A construct
$current-user would be harder
to interpret if hyphens were also allowed in variable names and, in
any case, would lead programs to be ambiguous.
Variable names are case-sensitive.
$This_Variable is not the same as
You cannot use spaces in variable names, as this would confuse
the PHP parser. Instead, try using the
To convert one variable type to another, reference it and PHP will automatically convert it for you.
There is no difference between
$j++ unless the value of
$j is being tested, assigned to another
variable, or passed as a parameter to a function. In such cases,