The
include() statement includes and evaluates the
specified file.
The documentation below also applies to
require(). The two constructs are identical in every
way except how they handle failure. include()
produces a
Warning while require() results in a Fatal Error. In
other words, use require() if you want a missing file to
halt processing of the page.
include() does not behave this
way, the script will continue regardless. Be sure to have an
appropriate
include_path setting as well.
When a file is included, the code it contains inherits
the variable
scope of the line on which the include occurs. Any
variables available at that line in the calling file will be
available within the called file, from that point
forward.
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If the include occurs inside a function within the
calling file, then all of the code contained in the called
file will behave as though it had been defined inside that
function. So, it will follow the variable scope of that
function.
When a file is included, parsing drops out of PHP mode
and into HTML mode at the beginning of the target file, and
resumes again at the end. For this reason, any code inside
the target file which should be executed as PHP code must be
enclosed within
valid PHP start and end tags.
If "URL fopen
wrappers" are enabled in PHP (which they are in the
default configuration), you can specify the file to be
included using an URL (via HTTP or other supported wrapper -
see 附錄 I for a list of protocols)
instead of a local pathname. If the target server interprets
the target file as PHP code, variables may be passed to the
included file using an URL request string as used with HTTP
GET. This is not strictly speaking the same thing as
including the file and having it inherit the parent file's
variable scope; the script is actually being run on the
remote server and the result is then being included into the
local script.
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Because include() and require()
are special language constructs, you must enclose them within
a statement block if it's inside a conditional block.
Handling Returns: It is possible to execute a return()
statement inside an included file in order to terminate
processing in that file and return to the script which called
it. Also, it's possible to return values from included files.
You can take the value of the include call as you would a
normal function.
注: In PHP 3, the return may not appear inside a block unless it's a function block, in which case the return() applies to that function and not the whole file.
$bar is the value 1 because the include was successful. Notice
the difference between the above examples. The first uses
return() within the included file while the other
does not. A few other ways to "include" files into variables
are with
fopen(), file() or by using include()
along with Output Control
Functions.
See also require(),
require_once(),
include_once(),
readfile(), virtual(), and
include_path.