PHP pclose Function

last modified April 3, 2025

The PHP pclose function closes a process file pointer opened by popen. It’s essential for proper resource cleanup when working with process pipes.

Basic Definition

The pclose function terminates the process associated with a pipe and closes the file pointer. It returns the termination status of the process.

Syntax: pclose(resource $handle): int. The function takes a pipe handle from popen and returns the process exit status.

Basic pclose Example

This shows the simplest usage of pclose with a process pipe.

basic_pclose.php

<?php

declare(strict_types=1);

$handle = popen(’ls -l’, ‘r’); if ($handle === false) { throw new RuntimeException(‘Failed to open process’); }

// Read process output here…

$status = pclose($handle);

echo “Process exited with status: $status”;

This opens a process to list files, then properly closes it with pclose. Always check if popen succeeded before calling pclose.

Reading Process Output Before Closing

This example reads output before closing the process.

read_before_close.php

<?php

declare(strict_types=1);

$handle = popen(‘date’, ‘r’); if ($handle === false) { throw new RuntimeException(‘Failed to open process’); }

$output = fread($handle, 4096); $status = pclose($handle);

echo “Output: $output”; echo “Exit status: $status”;

We read the process output before closing. The exit status is captured in $status. Always read all output before calling pclose.

Error Handling with pclose

This demonstrates proper error handling with process pipes.

error_handling.php

<?php

declare(strict_types=1);

$command = ’nonexistent-command 2>&1’; $handle = @popen($command, ‘r’);

if ($handle === false) { die(“Failed to execute command: $command”); }

$output = stream_get_contents($handle); $status = pclose($handle);

if ($status !== 0) { echo “Command failed with status $status\n”; echo “Error output: $output”; } else { echo “Command succeeded: $output”; }

This shows how to handle command failures. We capture both output and exit status. The 2>&1 redirects stderr to stdout for error capture.

Writing to a Process

This example demonstrates writing to a process before closing.

write_process.php

<?php

declare(strict_types=1);

$handle = popen(‘grep “error” > errors.log’, ‘w’); if ($handle === false) { throw new RuntimeException(‘Failed to open process’); }

fwrite($handle, “error: file not found\n”); fwrite($handle, “warning: deprecated function\n”); fwrite($handle, “error: permission denied\n”);

$status = pclose($handle);

echo “Grep process exited with status: $status”;

We open a process for writing, send data to it, then close it. The process filters input and writes to a file. Always close write pipes when done.

Checking Process Status

This example shows how to interpret the process exit status.

process_status.php

<?php

declare(strict_types=1);

function executeCommand(string $cmd): string { $handle = popen($cmd . ’ 2>&1’, ‘r’); if ($handle === false) { throw new RuntimeException(“Failed to execute: $cmd”); }

$output = stream_get_contents($handle);
$status = pclose($handle);

if ($status !== 0) {
    throw new RuntimeException(
        "Command failed with status $status: $output"
    );
}

return $output;

}

try { $result = executeCommand(’ls -l /nonexistent’); echo $result; } catch (RuntimeException $e) { echo “Error: " . $e->getMessage(); }

This wraps process execution in a function with proper error handling. The exit status is checked after closing. Non-zero status indicates command failure.

Best Practices

• Always Close: Never leave process pipes open.

• Error Handling: Check both popen and pclose results.

• Resource Limits: Be mindful of system process limits.

• Security: Sanitize command inputs to prevent injection.

• Timeouts: Consider adding timeouts for long-running processes.

Source

PHP pclose Documentation

This tutorial covered the PHP pclose function with practical examples showing its usage with process pipes in different scenarios.

Author

My name is Jan Bodnar, and I am a passionate programmer with extensive programming experience. I have been writing programming articles since 2007. To date, I have authored over 1,400 articles and 8 e-books. I possess more than ten years of experience in teaching programming.

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