PHP Filesystem popen() Function

---

---

The PHP Filesystem popen() function is used to open a pipe to the program specified in the command parameter, and return false if an error occurs. This function mainly allows us to execute a command given inside the function and read its output or write input to it.

The opened pointer can be accessible using fgets(), fgetss(), and fwrite(). When the mode is 'r', the returned file pointer equals the command's STDOUT; when the mode is 'w', the returned file pointer equals the command's STDIN.

Syntax

Below is the syntax of the PHP Filesystem popen() function −

resource popen ( string $command , string $mode )

Parameters

Below are the required and optional parameters of the popen() function −

Return Value

The function popen() returns a unidirectional file reference that is similar to that returned by fopen(), with the exception that it can only be used for reading or writing. If an error occurs, return false.

PHP Version

The popen() function was first introduced as part of core PHP 4 and work well with the PHP 5, PHP 7 and PHP 8.

Example

Here is the basic example to see how the PHP Filesystem popen() function is used to open a pipe.

<?php
   //Open a pipe
   $handle = popen("/bin/ls", "r");

   //Close the pipe
   pclose($handle);
?>

If the command to be executed cannot be found, a valid resource is returned. This may seem odd, but it makes sense: it allows you to get any error message returned by the shell.

Output

Here is the outcome of the following code −

ls: stdout: Broken pipe

Example

Here is the another example to show the usage of popen() function to open a pipe by handling error.

<?php
   // Open a pipe
   $handle = popen("/bin/ls", "r");

   if ($handle) {
      // Read the output from the pipe
      while (($line = fgets($handle)) !== false) {
         echo $line;
      }

      // Close the pipe
      popen($handle);
   } else {
      echo "We are unable to open the pipe.";
   }
?> 

Output

This will produce the following result −

config.php
csvfile.csv
data.csv
documents
error_log.log
image.jpg
images
index.php
logo.gif
logs
myfile.txt
new dir

Example

Here is one more example to know the usage of popen() function. So we will read the contents of a file by using the cat command. We will write the file name to the cat command.

<?php
   // Open a pipe
   $handle = popen("cat", "w"); // "w" means write

   if ($handle) {
      fwrite($handle, "PhpProjects/myfile.txt"); // Here write the file name to the command
      
      // Close the process
      pclose($handle); 
   } else {
      echo "We are unable to open process.";
   }
?> 

Output

This will generate the below output −

PhpProjects/myfile.txt

Note

On Windows, popen() defaults to text mode, which means that any \n characters written to or read from the pipe are translated to \r\n. If this is not wished binary mode can be enabled by setting mode to 'rb' or 'wb'.

Summary

The popen() method is a built-in function used to open a pipe to the process executed by forking the command given by command.