PHP uses recursion to list all files and directories

What is Recursion

The programming technique in which a program calls itself is called recursion. Recursion as an algorithm is widely used in programming languages. A procedure or function has a method of directly or indirectly calling itself in its definition or description. It usually transforms a large and complex problem into a smaller problem similar to the original problem. To solve the problem, the recursive strategy only needs a small amount of programs to describe the multiple repeated calculations required in the problem-solving process, greatly reducing the amount of program code. The power of recursion lies in defining an infinite collection of objects with a finite number of statements. Generally speaking, recursion requires boundary conditions, a recursive forward segment, and a recursive return segment. When the boundary conditions are not met, the recursion advances; when the boundary conditions are met, the recursion returns.

The following example is php using recursion to list all files and directories

<?php 

function tree($directory) 
{ 
$mydir=dir($directory); 
echo "<ul> 
"; 
while($file=$mydir->read()){ 
if((is_dir("$directory/$file")) AND ($file!=".") AND ($file!="..")) 
{echo "<li><font color="#ff00cc"><b>$file</b></font></li> 
"; 
tree("$directory/$file"); 
} 
else 
echo "<li>$file</li> 
"; 
} 
echo "</ul> 
"; 
$mydir->close(); 
} 
//start the program 
echo "<h2>目录为粉红色</h2> 
"; 
tree("."); 
?>

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