PHP File Handling

PHP File Handling & Operations (readfile(), file_get_contents())

PHP provides simple high-level functions for inspecting files, checking file existence, reading file contents into memory strings, and piping file streams directly to the HTTP output response.

Core High-Level File Functions

• file_exists($path): Returns true if file or directory exists.
• is_file($path): Returns true if target path is a regular file.
• filesize($path): Returns file size in bytes.
• readfile($path): Reads file and writes content directly to output buffer (ideal for downloads).
• file_get_contents($path): Reads entire file content into a PHP string variable.

flowchart TD
    A["File System Path Check"] --> B{"file_exists($file)"}
    B -- False --> C["Return File Not Found Error"]
    B -- True --> D{"Choose Read Strategy"}
    D -- Memory String --> E["$content = file_get_contents($file)"]
    D -- Direct Stream Download --> F["readfile($file)"]

Practical Code Example

<?php
declare(strict_types=1);

$filePath = __DIR__ . '/sample_log.txt';

// Create temporary sample file if not present
if (!file_exists($filePath)) {
    file_put_contents($filePath, "2026-08-13 10:00:00 | SYSTEM_INIT | Service started successfully.
");
}

// 1. File Inspection
if (file_exists($filePath) && is_file($filePath)) {
    $bytes = filesize($filePath);
    echo "Target File: " . basename($filePath) . " ($bytes bytes)
";

    // 2. Reading entire file content into string
    $fileData = file_get_contents($filePath);
    echo "--- File Contents ---
" . $fileData;
} else {
    echo "Error: Target file does not exist.
";
}

Best Practices

• Check file_exists() Before Reading: Always verify file existence to avoid E_WARNING file access errors.
• Use file_get_contents() for Small-to-Medium Files: Simple and fast for reading files under a few megabytes into memory strings.
• Use Stream Buffering for Huge Files (>50MB): Do not load multi-gigabyte log files into memory with file_get_contents(); stream them line-by-line using fopen() and fgets().

Self-Check Challenge

Write a PHP script that checks if config.json exists using file_exists(), and if so, reads its content into $jsonString using file_get_contents()!