proc_open
(PHP 4 >= 4.3.0, PHP 5, PHP 7, PHP 8)
proc_open — Execute a command and open file pointers for input/output
Description
array|string
$command,array
$descriptor_spec,array
&$pipes,?string
$cwd = null,?array
$env_vars = null,?array
$options = null): resource|false
proc_open() is similar to popen() but provides a much greater degree of control over the program execution.
Parameters
-
command -
The commandline to execute as string. Special characters have to be properly escaped, and proper quoting has to be applied.
Note: On Windows, unless
bypass_shellis set totrueinoptions, thecommandis passed to cmd.exe (actually,%ComSpec%) with the/cflag as unquoted string (i.e. exactly as has been given to proc_open()). This can cause cmd.exe to remove enclosing quotes fromcommand(for details see the cmd.exe documentation), resulting in unexpected, and potentially even dangerous behavior, because cmd.exe error messages may contain (parts of) the passedcommand(see example below).As of PHP 7.4.0,
commandmay be passed as array of command parameters. In this case the process will be opened directly (without going through a shell) and PHP will take care of any necessary argument escaping.Note:
On Windows, the argument escaping of the array elements assumes that the command line parsing of the executed command is compatible with the parsing of command line arguments done by the VC runtime.
-
descriptor_spec -
An indexed array where the key represents the descriptor number and the value represents how PHP will pass that descriptor to the child process. 0 is stdin, 1 is stdout, while 2 is stderr.
Each element can be:
- An array describing the pipe to pass to the process. The first
element is the descriptor type and the second element is an option for
the given type. Valid types are
pipe(the second element is eitherrto pass the read end of the pipe to the process, orwto pass the write end) andfile(the second element is a filename). Note that anything else thanwis treated liker. -
A stream resource representing a real file descriptor (e.g. opened file,
a socket,
STDIN).
The file descriptor numbers are not limited to 0, 1 and 2 - you may specify any valid file descriptor number and it will be passed to the child process. This allows your script to interoperate with other scripts that run as "co-processes". In particular, this is useful for passing passphrases to programs like PGP, GPG and openssl in a more secure manner. It is also useful for reading status information provided by those programs on auxiliary file descriptors.
- An array describing the pipe to pass to the process. The first
element is the descriptor type and the second element is an option for
the given type. Valid types are
-
pipes -
Will be set to an indexed array of file pointers that correspond to PHP's end of any pipes that are created.
-
cwd -
The initial working dir for the command. This must be an absolute directory path, or
nullif you want to use the default value (the working dir of the current PHP process) -
env_vars -
An array with the environment variables for the command that will be run, or
nullto use the same environment as the current PHP process -
options -
Allows you to specify additional options. Currently supported options include:
-
suppress_errors(windows only): suppresses errors generated by this function when it's set totrue -
bypass_shell(windows only): bypasscmd.exeshell when set totrue -
blocking_pipes(windows only): force blocking pipes when set totrue -
create_process_group(windows only): allow the child process to handleCTRLevents when set totrue -
create_new_console(windows only): the new process has a new console, instead of inheriting its parent's console
-
Return Values
Returns a resource representing the process, which should be freed using
proc_close() when you are finished with it. On failure
returns false.
Changelog
| Version | Description |
|---|---|
| 7.4.4 |
Added the create_new_console option to the
options parameter.
|
| 7.4.0 |
proc_open() now also accepts an array
for the command.
|
| 7.4.0 |
Added the create_process_group option to the
options parameter.
|
Examples
Example #1 A proc_open() example
<?php
$descriptorspec = array(
0 => array("pipe", "r"), // stdin is a pipe that the child will read from
1 => array("pipe", "w"), // stdout is a pipe that the child will write to
2 => array("file", "/tmp/error-output.txt", "a") // stderr is a file to write to
);
$cwd = '/tmp';
$env = array('some_option' => 'aeiou');
$process = proc_open('php', $descriptorspec, $pipes, $cwd, $env);
if (is_resource($process)) {
// $pipes now looks like this:
// 0 => writeable handle connected to child stdin
// 1 => readable handle connected to child stdout
// Any error output will be appended to /tmp/error-output.txt
fwrite($pipes[0], '<?php print_r($_ENV); ?>');
fclose($pipes[0]);
echo stream_get_contents($pipes[1]);
fclose($pipes[1]);
// It is important that you close any pipes before calling
// proc_close in order to avoid a deadlock
$return_value = proc_close($process);
echo "command returned $return_value\n";
}
?>
The above example will output something similar to:
Array
(
[some_option] => aeiou
[PWD] => /tmp
[SHLVL] => 1
[_] => /usr/local/bin/php
)
command returned 0
Example #2 proc_open() quirk on Windows
While one may expect the following program to search the file
filename.txt for the text search and
to print the results, it behaves rather differently.
<?php
$descriptorspec = [STDIN, STDOUT, STDOUT];
$cmd = '"findstr" "search" "filename.txt"';
$proc = proc_open($cmd, $descriptorspec, $pipes);
proc_close($proc);
?>
The above example will output:
'findstr" "search" "filename.txt' is not recognized as an internal or external command, operable program or batch file.
To work around that behavior, it is usually sufficient to enclose the
command in additional quotes:
$cmd = '""findstr" "search" "filename.txt""';
Notes
Note:
Windows compatibility: Descriptors beyond 2 (stderr) are made available to the child process as inheritable handles, but since the Windows architecture does not associate file descriptor numbers with low-level handles, the child process does not (yet) have a means of accessing those handles. Stdin, stdout and stderr work as expected.
Note:
If you only need a uni-directional (one-way) process pipe, use popen() instead, as it is much easier to use.
See Also
- popen() - Opens process file pointer
- exec() - Execute an external program
- system() - Execute an external program and display the output
- passthru() - Execute an external program and display raw output
- stream_select() - Runs the equivalent of the select() system call on the given arrays of streams with a timeout specified by seconds and microseconds
- The backtick operator
