PHP tmpfile Function

last modified April 3, 2025

The PHP tmpfile function creates a temporary file with a unique name in read-write (w+) mode. The file is automatically deleted when closed or when the script ends.

Basic Definition

The tmpfile function creates a temporary file and returns a file handle. The file is created with unique name in the system's temp directory.

Syntax: tmpfile(): resource|false. Returns file handle on success or false on failure. The file is removed when fclose() is called or script ends.

Basic tmpfile Example

This shows the simplest usage of tmpfile to create a temp file.

basic_tmpfile.php

<?php

declare(strict_types=1);

$tempFile = tmpfile();

if ($tempFile === false) {
    die("Failed to create temporary file");
}

fwrite($tempFile, "Hello, temporary file!");
rewind($tempFile);
echo fread($tempFile, 1024);

fclose($tempFile); // File is automatically deleted

This creates a temp file, writes to it, reads back the content, then closes it. The file is deleted when fclose() is called or when the script terminates.

Writing Structured Data

Temporary files can store structured data like JSON or serialized PHP.

structured_data.php

<?php

declare(strict_types=1);

$tempFile = tmpfile();
$data = ['name' => 'John', 'age' => 30, 'city' => 'New York'];

fwrite($tempFile, json_encode($data));
rewind($tempFile);

$content = fread($tempFile, 1024);
$decoded = json_decode($content, true);

print_r($decoded);
fclose($tempFile);

This example stores an array as JSON in a temp file, then reads it back. Temp files are useful for intermediate data processing without permanent storage.

Stream Operations

Temporary files support all standard stream operations like fseek and ftell.

stream_operations.php

<?php

declare(strict_types=1);

$tempFile = tmpfile();
fwrite($tempFile, "ABCDEFGHIJKLMNOPQRSTUVWXYZ");

fseek($tempFile, 10, SEEK_SET);
echo fread($tempFile, 5); // Outputs: KLMNO

echo "\nCurrent position: " . ftell($tempFile); // 15
fclose($tempFile);

This demonstrates seeking within the temp file and reading from a specific position. The file pointer position can be tracked with ftell().

Error Handling

Proper error handling is important when working with temporary files.

error_handling.php

<?php

declare(strict_types=1);

$tempFile = @tmpfile();

if ($tempFile === false) {
    $error = error_get_last();
    echo "Error creating temp file: " . $error['message'];
    exit(1);
}

try {
    if (fwrite($tempFile, "Test data") === false) {
        throw new RuntimeException("Write failed");
    }
    // Process file...
} finally {
    if (is_resource($tempFile)) {
        fclose($tempFile);
    }
}

This shows robust error handling for temp file creation and operations. The finally block ensures the file is properly closed even if an error occurs.

Multiple Temp Files

You can create and manage multiple temporary files in a single script.

multiple_files.php

<?php

declare(strict_types=1);

$file1 = tmpfile();
$file2 = tmpfile();

fwrite($file1, "Data for file 1");
fwrite($file2, "Data for file 2");

rewind($file1);
rewind($file2);

echo "File 1: " . fread($file1, 1024) . "\n";
echo "File 2: " . fread($file2, 1024) . "\n";

fclose($file1);
fclose($file2);

This creates two independent temp files with different content. Each temp file gets a unique name and can be managed separately before being automatically deleted.

Best Practices

Error Checking: Always verify tmpfile() doesn't return false.
Resource Management: Close files explicitly when done.
Memory Efficiency: Use for large data instead of memory.
Security: Temp files are more secure than fixed names.
Cleanup: Rely on automatic deletion but verify if needed.

Source

PHP tmpfile Documentation

This tutorial covered the PHP tmpfile function with practical examples showing its usage for temporary data storage and processing.

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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