PHP tempnam Function

last modified April 3, 2025

The PHP tempnam function creates a temporary file with a unique name. It's useful for creating temporary storage that won't conflict with existing files.

Basic Definition

The tempnam function creates a file with a unique name in the specified directory. It returns the path to the newly created file.

Syntax: tempnam(string $directory, string $prefix): string|false. The function returns false on failure. The created file is empty and has 0600 permissions.

Basic tempnam Example

This shows the simplest usage of tempnam to create a temporary file.

basic_tempnam.php

<?php

declare(strict_types=1);

$tempFile = tempnam(sys_get_temp_dir(), 'TMP_');

echo "Temporary file created: " . $tempFile;

This creates a temporary file in the system temp directory with 'TMP_' prefix. The file is automatically assigned a unique name to prevent collisions.

Custom Directory Example

You can specify a custom directory for the temporary file creation.

custom_directory.php

<?php

declare(strict_types=1);

$customDir = '/var/tmp/';
$tempFile = tempnam($customDir, 'APP_');

if ($tempFile !== false) {
    echo "Custom temp file: " . $tempFile;
} else {
    echo "Failed to create temp file";
}

Here we create a temp file in '/var/tmp/' with 'APP_' prefix. Always check the return value as the function may fail if directory doesn't exist or isn't writable.

Writing to Temporary File

This example shows how to write data to the created temporary file.

write_temp_file.php

<?php

declare(strict_types=1);

$tempFile = tempnam(sys_get_temp_dir(), 'DATA_');

if ($tempFile !== false) {
    file_put_contents($tempFile, "Temporary data storage\n");
    echo "Data written to: " . $tempFile;
    
    // Remember to clean up when done
    unlink($tempFile);
}

We create a temp file and write data to it. Note we manually delete the file when done. Temporary files aren't automatically removed by PHP.

Secure Temporary File Handling

This example demonstrates secure handling of temporary files with error checking.

secure_tempnam.php

<?php

declare(strict_types=1);

$tempDir = sys_get_temp_dir();
if (!is_writable($tempDir)) {
    throw new RuntimeException("Temp directory not writable");
}

$tempFile = tempnam($tempDir, 'SEC_');
if ($tempFile === false) {
    throw new RuntimeException("Failed to create temp file");
}

try {
    // Use the temp file
    file_put_contents($tempFile, "Sensitive data");
    // Process the file...
} finally {
    if (file_exists($tempFile)) {
        unlink($tempFile);
    }
}

This shows robust temp file handling with directory checks, error handling, and guaranteed cleanup. The finally block ensures file deletion even if errors occur.

Temp File with Specific Extension

This example creates a temp file with a specific extension by renaming.

temp_with_extension.php

<?php

declare(strict_types=1);

$tempFile = tempnam(sys_get_temp_dir(), 'TMP_');
$newName = $tempFile . '.txt';

if (rename($tempFile, $newName)) {
    echo "Created temp file with extension: " . $newName;
    // Remember to clean up
    unlink($newName);
} else {
    unlink($tempFile);
    echo "Failed to rename temp file";
}

We first create a temp file then rename it to add an extension. If renaming fails, we clean up the original temp file to avoid leaving unused files.

Best Practices

Clean up: Always delete temp files when done.
Error handling: Check return values for failures.
Permissions: Verify directory is writable first.
Security: Use proper permissions (0600 by default).
Atomicity: tempnam guarantees unique file creation.

Source

PHP tempnam Documentation

This tutorial covered the PHP tempnam function with practical examples showing its usage for creating temporary files securely.

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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