PHP does not recursively traverse the code of all files in the directory _php tutorial

Implementation code:

/** * PHP non-recursive implementation query all files under this directory * @param unknown $dir * @return multitype:|multitype:string */function scanfiles ($dir) {if (! I S_dir ($dir)) return array ();  Compatible with each operating system $dir = RTrim (str_replace (' \ \ ', '/', $dir), '/'). '/';  Stack, the default value is the incoming directory $dirs = array ($dir);  The container where all the files are placed $rt = Array ();  do {//Stack $dir = Array_pop ($dirs);  Scan this directory $tmp = Scandir ($dir);  foreach ($tmp as $f) {  //filter ...  if ($f = = '. ' | | $f = = ' ... ')  Continue;    Combines the current absolute path  $path = $dir. $f;      If it is a directory, press stack.  if (Is_dir ($path)) {  Array_push ($dirs, $path. '/' );  }  else if (Is_file ($path)) {///If it is a file, put in the container  $rt [] = $path;}}  } while ($dirs);//until there is no directory return in the stack  $rt;}

Attach another article: Do not recursively traverse the file under the directory

If you want to traverse all files (including subdirectories) in a directory, the first idea is to use recursion: Process the current directory first, and then process the subdirectories under the current directory. Can you do it without recursion? Before learning the data structure to see, recursion is actually the use of the stack to achieve, recursive feature is the constant call itself, the last call is the first to execute, the penultimate call is the second execution, and so on, the original call is the last execution. If we understand the principle of recursion, we can turn all the implementations of recursion into non-recursive implementations.

To traverse all files in a directory in a non-recursive way, the idea is divided into three main steps:

1. Create an array to put in the directory that will be traversed; (in fact, create a stack)
2. Loop through this array, the condition of the loop end is that the array is empty;
3. Each loop, processing an element in the array, and delete the element, if the element is a directory, then the directory of all the child elements are added to the array;

The code written in this way is as follows:

/** * Traverse all files in a directory * @param string $dir */function scanAll ($dir) {  $list = array ();  $list [] = $dir;  while (count ($list) > 0)  {    //popup array last element    $file = Array_pop ($list);    Handles the current file    echo $file. \ r \ n ";    If it is a directory if    (Is_dir ($file))    {      $children = Scandir ($file);      foreach ($children as $child)      {        if ($child!== '. ' && $child!== ')        {          $list [] = $file. ' /'. $child;}}}}  

I do not think there are many disadvantages of recursion, in fact, in many cases, the return design is very concise and readable, as for the efficiency problem, unless the recursion depth is particularly large, it will have an impact.

The following is a recursive implementation, as a comparison:

/** * Traverse all files in a directory (recursive implementation) * @param string $dir */function scanAll2 ($dir) {  echo $dir. " \ r \ n ";  if (Is_dir ($dir))  {    $children = Scandir ($dir);    foreach ($children as $child)    {      if ($child!== '. ' && $child!== ')      {        scanAll2 ($dir. '/'. $child);}}}}  

Running found that the results of the two functions are slightly different, mainly in the order of printing. The order of the function's results is reversed because the order of the stacks is exactly the opposite of the order of the Scandir, and the 21st line can be changed:

$children = Array_reverse (Scandir ($file));

So the result is exactly the same.

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