PHP | popen( ) Function

The popen() function used to open a pipe to the program specified by the user using the command parameter. It returns a file pointer which is identical to that returned by fopen(), but it is unidirectional in nature i.e it can be only used for reading or writing. The popen() pointer can be used with fgets(), fgetss(), and fwrite(). The file pointer initiated by the popen() function must be closed with pclose().
The command and the mode are sent as parameters to the popen() function and it returns a unidirectional file pointer on success or FALSE on failure.

Syntax:

popen(command, mode)

Parameters Used:
The popen() function in PHP accepts two parameters.

1. command : It is a mandatory parameter which specifies the command to be executed.
2. mode : It is a mandatory parameter which specifies the connection mode such as read only(r) or write only(w).

Return Value:
It returns a file pointer which is identical to that returned by fopen(), but it is unidirectional in nature.

Errors And Exceptions:

1. The file pointer initiated by the popen() function must be closed with pclose().
2. If the command to be executed could not be found, then the popen() function returns a valid resource.

Examples:

Input : $my_file= popen("/bin/ls", "r");
Output : 1

Input : $my_file= popen('/executable/gfg.exe', 'r');
        echo "'my_file'; " . get_class($my_handle) . "\n";
        $file_read = fread($my_file, 4192);
        echo $file_read;
        pclose($my_file);
Output : 1

Below programs illustrate the popen() function.

Program 1

<?php

// opening a pipe
$my_file= popen("/bin/ls", "r");
?>

Output:

1

Program 2

<?php
// opening a pipe
$my_file= popen('/executable/gfg.exe', 'r');

// returning name of class of an object using get_class()
  echo "'$my_file'; " . get_class($my_file) . "\n";

// reading file using fread()
$filereader = fread($my_file, 4192);
   echo $filereader;

// closing the pipe
pclose($my_file);
?>

Output:

1

Reference:
http://php.net/manual/en/function.popen.php