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File Input & Output

⏱ 20 min read read

Quick File Functions (Most Common):

// Write entire file at once

file_put_contents('notes.txt', "Hello!\nLine 2\n");

// Read entire file at once

$content = file_get_contents('notes.txt');

// Read into array of lines

$lines = file('notes.txt', FILE_IGNORE_NEW_LINES);

// Check if file exists

file_exists('notes.txt'); // true or false

fopen / fclose (Stream API):

// Modes: r=read, w=write(overwrite), a=append, x=create(fail if
exists)

$handle = fopen('notes.txt', 'w');

fwrite($handle, "Hello!\n");

fclose($handle);

// Reading line by line

$handle = fopen('notes.txt', 'r');

while (($line = fgets($handle)) !== false) {

echo trim($line) . "\n";

}

fclose($handle);

CSV Files:

// Write CSV

$handle = fopen('grades.csv', 'w');

fputcsv($handle, ['Name', 'Grade']); // header

fputcsv($handle, ['Alice', 92]);

fclose($handle);

// Read CSV

$handle = fopen('grades.csv', 'r');

$header = fgetcsv($handle); // read header row

while (($row = fgetcsv($handle)) !== false) {

[$name, $grade] = $row;

echo "$name: $grade\n";

}

fclose($handle);

JSON Files:

// Write JSON

$data = ['name' => 'Alice', 'age' => 25, 'scores' =>
[92, 85, 88]];

file_put_contents('data.json', json_encode($data,
JSON_PRETTY_PRINT));

// Read JSON

$loaded = json_decode(file_get_contents('data.json'), true); //
true = assoc array

echo $loaded['name'] . "\n";

Code Example

<?php

// Simple file write / read

file_put_contents('notes.txt', "Hello!\nLine 2\nLine 3\n");

echo "notes.txt written!\n";

$content = file_get_contents('notes.txt');

echo $content;

// Read lines into array

$lines = file('notes.txt', FILE_IGNORE_NEW_LINES);

foreach ($lines as $i => $line) {

echo " " . ($i+1) . ": $line\n";

}

// Append to file

file_put_contents('notes.txt', "Line 4\n", FILE_APPEND);

// CSV grade tracker --- WRITE

$grades = ['Alice' => 92, 'Bob' => 78, 'Carol' => 88];

$handle = fopen('grades.csv', 'w');

fputcsv($handle, ['Name', 'Grade']);

foreach ($grades as $name => $grade) {

fputcsv($handle, [$name, $grade]);

}

fclose($handle);

// CSV grade tracker --- READ

$handle = fopen('grades.csv', 'r');

$header = fgetcsv($handle); // skip header

while (($row = fgetcsv($handle)) !== false) {

[$name, $grade] = $row;

$status = (int)$grade >= 70 ? 'Pass' : 'Fail';

echo "$name: $grade --- $status\n";

}

fclose($handle);

// JSON write and read

$data = ['name' => 'Alice', 'age' => 25, 'scores' =>
[92, 85, 88]];

file_put_contents('data.json', json_encode($data,
JSON_PRETTY_PRINT));

$loaded = json_decode(file_get_contents('data.json'), true);

echo "Loaded: {$loaded['name']}, age
{$loaded['age']}\n";

// Directory operations

if (!is_dir('uploads')) mkdir('uploads');

$files = scandir('.');

foreach ($files as $f) {

if ($f !== '.' && $f !== '..') echo $f . "\n";

}

// Cleanup

unlink('notes.txt');

unlink('grades.csv');

unlink('data.json');

?>

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