PHP fscanf Function

last modified April 3, 2025

The PHP fscanf function reads formatted input from a file. It’s similar to scanf but works with file resources instead of stdin.

Basic Definition

The fscanf function parses input from a file according to a format. It takes a file handle and format string as required parameters.

Syntax: fscanf(resource $handle, string $format, mixed &…$vars): mixed. The function returns the number of assigned values or false on failure.

Basic fscanf Example

This shows the simplest usage of fscanf to read a single value.

basic_fscanf.php

<?php

declare(strict_types=1);

$file = fopen(“data.txt”, “r”); if ($file === false) { die(“Error opening file”); }

$count = fscanf($file, “%d”); fclose($file);

echo “Read value: " . $count[0];

This reads an integer from “data.txt”. The format specifier “%d” matches a decimal integer. The result is returned as an array.

Reading Multiple Values

fscanf can read multiple values at once using a format string.

multi_value.php

<?php

declare(strict_types=1);

$file = fopen(“user.txt”, “r”); if ($file === false) { die(“Error opening file”); }

$result = fscanf($file, “%s %d %f”); fclose($file);

[$name, $age, $score] = $result;

echo “Name: $name, Age: $age, Score: $score”;

This reads a string, integer, and float from the file. The values are assigned to variables using array destructuring for cleaner code.

Using Variable References

Instead of returning an array, fscanf can assign to variables.

variable_references.php

<?php

declare(strict_types=1);

$file = fopen(“product.txt”, “r”); if ($file === false) { die(“Error opening file”); }

$id = 0; $name = “”; $price = 0.0;

$count = fscanf($file, “%d %s %f”, $id, $name, $price); fclose($file);

echo “Read $count values: ID $id, $name, $$price”;

Here we pass variables by reference to receive the parsed values directly. The function returns the count of successfully assigned values.

Complex Format String

fscanf supports complex format strings with literal characters.

complex_format.php

<?php

declare(strict_types=1);

$file = fopen(“log.txt”, “r”); if ($file === false) { die(“Error opening file”); }

$date = “”; $time = “”; $message = “”;

fscanf($file, “[%10s %8s] %[^\n]”, $date, $time, $message); fclose($file);

echo “On $date at $time: $message”;

This parses a log file entry with a specific format. The “%[^\n]” specifier matches all characters until a newline. Literal brackets are part of the format.

Reading Until EOF

We can use fscanf in a loop to process all data in a file.

read_until_eof.php

<?php

declare(strict_types=1);

$file = fopen(“numbers.txt”, “r”); if ($file === false) { die(“Error opening file”); }

$sum = 0; while (fscanf($file, “%d”, $number) === 1) { $sum += $number; } fclose($file);

echo “Sum of numbers: $sum”;

This reads integers from a file until EOF. The loop continues as long as fscanf successfully reads one value per line.

Best Practices

• Error Handling: Always check if file opening succeeds.

• Resource Management: Close files with fclose.

• Type Safety: Use strict_types for predictable behavior.

• Format Validation: Verify input matches expected format.

Source

PHP fscanf Documentation

This tutorial covered the PHP fscanf function with practical examples showing its usage for formatted file input.

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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