Why would I use dirname FILE in an include or include once statement

Question

I have seen this     lt  php   include  dirname   FILE      DIRECTORY SEPARATOR    my file php      gt    Why would I ever need to do this  Why would I go to the trouble of getting the dirname and then concatenating that with a directory separator  and a new filename    Is the code above not equivalent to this     lt  php   include   my file php       gt        The PHP doc says       Files are included based on the file path given or  if none is given  the include path specified  If the file isn t found in the include path  include   will finally check in the calling script s own directory and the current working directory before failing  The include   construct will emit a warning if it cannot find a file  this is different behavior from require    which will emit a fatal error

User · Answer

I used this below if this is what you are thinking. It it worked well for me.

<?php
    include $_SERVER['DOCUMENT_ROOT']."/head_lib.php";
?>

What I was trying to do was pulla file called /head_lib.php from the root folder. It would not pull anything to build the webpage. The header, footer and other key features in sub directories would never show up. Until I did above it worked like a champ.

User · Answer

Let s say I have a  fake  directory structure like       root           app             bootstrap php          scripts             something                  somescript php          public             index php   Now assume that bootstrap php has some code included for setting up database connections or some other kind of boostrapping stuff   Assume you want to include a file in boostrap php s folder called init php   Now  to avoid scanning the entire include path with include  init php   you could use include    init php    There s a problem though  That    will be relative to the script that included bootstrap php  not bootstrap php   Technically speaking  it will be relative to the working directory    dirname   FILE    allows you to get an absolute path  and thus avoid an include path search  without relying on the working directory being the directory in which bootstrap php resides    Note  since PHP 5 3  you can use   DIR   in place of dirname   FILE       Now  why not just use include  init php      As odd as it is at first though    is not guaranteed to be in the include path   Sometimes to avoid useless stat   s people remove it from the include path when they are rarely include files in the same directory  why search the current directory when you know includes are never going to be there     Note  About half of this answer is address in a rather old post  What  39 s better of require dirname   FILE      39    39    39 myParent php  39   than just require   39 myParent php  39

User · Answer

If you want code is running on multiple servers with different environments then we have need   to use dirname FILE  in an include or include once statement   reason is follows  1  Do not give absolute path to include files on your server  2  Dynamically calculate the full path like absolute path   Use a combination of dirname FILE  and subsequent calls to itself until you reach to the home of your   myfile php    Then attach this variable that contains the path to your included files

User · Answer

I might have even a simpler explanation to this question compared to the accepted answer so I m going to give it a go  Assume this is the structure of the files and directories of a project   Project root directory                         file1 php                        file3 php                        dir1                              file2 php    dir1 is a directory and file2 php is inside it   And this is the content of each of the three files above     file1 php   lt  php include  dir1 file2 php     file2 php   lt  php include     file3 php     file3 php   lt  php echo  Hello  Test      Now run file1 php and try to guess what should happen  You might expect to see  Hello  Test    however  it won t be shown  What you ll get instead will be an error indicating that the file you have requested file3 php  does not exist   The reason is that  inside file1 php when you include file2 php  the content of it is getting copied and then pasted back directly into file1 php which is inside the root directory  thus this part     file3 php  runs from the root directory and thus goes one directory up the root   and obviously it won t find the file3 php    Now  what should we do     Relative paths of course have the problem above  so we have to use absolute paths  However  absolute paths have also one problem  If you  for example  copy the root folder  containing your whole project  and paste it in anywhere else on your computer  the paths will be invalid from that point on  And that ll be a REAL MESS   So we kind of need paths that are both absolute and dynamic Each file dynamically finds the absolute path of itself wherever we place it    The way we do that is by getting help from PHP  and dirname   is the function to go for  which gives the absolute path to the directory in which a file exists in  And each file name could also be easily accessed using the   FILE   constant  So dirname   FILE    would easily give you the absolute  while dynamic   path to the file we re typing in the above code  Now move your whole project to a new place  or even a new system  and tada  it works   So now if we turn the project above to this     file1 php   lt  php include dirname   FILE      dir1 file2 php       file2 php   lt  php include dirname   FILE         file3 php       file3 php   lt  php echo  Hello  Test      if you run it  you ll see the almighty Hello  Test    hopefully  if you ve not done anything else wrong    It s also worth mentioning that from PHP5  a nicer way with regards to readability and preventing eye boilage   has been provided by PHP as well which is the constant   DIR   which does exactly the same thing as dirname   FILE      Hope that helps

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