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