PHP File Open/Read

Before PHP can read data out of a file on the server, it first needs a way to open that file and get a handle to it -- a reference PHP uses for every subsequent read operation. fopen() opens the file and returns that handle, and a family of related functions (fread, fgets, fgetcsv, and more) read its contents in different ways.

In this page:

Opening a File with fopen()
Reading the Whole File with file_get_contents()
Reading Line by Line with fgets()
Reading a File into an Array with file()
Reading a Specific Number of Bytes with fread()

Syntax

php

$handle = fopen("filename.txt", "r");
$line = fgets($handle);   // read one line
fclose($handle);

$content = file_get_contents("filename.txt");

Opening a File with fopen()

fopen($filename, $mode) opens the given file and returns a resource handle representing that open file -- "r" mode opens it for reading only, positioned at the very start of the file, ready for the read functions that follow.

Note: Always store the return value of fopen() and check it is not false before using it, since a missing file or permission problem causes fopen() to fail silently otherwise.

Warning: Opening a file that does not exist in "r" mode returns false rather than throwing an exception, so an unchecked fopen() failure often surfaces later as a confusing error on the next line.

Example: Opening a File with fopen()

php

<?php
// Call `file_put_contents("data.txt", "Sample content")`
file_put_contents("data.txt", "Sample content");
// Declare `$handle`, set to `fopen("data.txt", "r")`
$handle = fopen("data.txt", "r");
// Print `$handle ? "File opened" : "Failed"` to the output
echo $handle ? "File opened" : "Failed";
// Call `fclose($handle)`
fclose($handle);
?>

Reading the Whole File with file_get_contents()

file_get_contents($filename) reads an entire file into a single string in one call, without needing fopen(), a read loop, or fclose() at all -- the simplest option when you just need the whole file's contents at once and the file is not too large.

Note: Use file_get_contents() as your default for smaller files where loading everything into memory at once is not a concern.

Warning: file_get_contents() loads the entire file into memory in one go, which can be a problem for very large files -- fopen() with a read loop is more appropriate there.

Example: Reading the Whole File with file_get_contents()

php

<?php
// Call `file_put_contents("data.txt", "Full file contents")`
file_put_contents("data.txt", "Full file contents");
// Print `file_get_contents("data.txt")` to the output
echo file_get_contents("data.txt");
?>

Reading Line by Line with fgets()

fgets($handle) reads a single line from an open file handle, moving the file pointer to the start of the next line each time it is called -- looping fgets() until it returns false is the standard way to process a file one line at a time without loading it all into memory at once.

Note: Prefer fgets() in a loop over file_get_contents() for very large files, since it only holds one line in memory at a time.

Warning: fgets() returns false once the end of the file is reached -- forgetting this exit condition in a while loop can cause the loop to run forever.

Example: Reading Line by Line with fgets()

php

<?php
// Call `file_put_contents("data.txt", "Line 1\nLine 2\nLine 3")`
file_put_contents("data.txt", "Line 1\nLine 2\nLine 3");
// Declare `$handle`, set to `fopen("data.txt", "r")`
$handle = fopen("data.txt", "r");
// Keep looping while `($line = fgets($handle)) !== false` holds
while (($line = fgets($handle)) !== false) {
    // Print `$line` to the output
    echo $line;
}
// Call `fclose($handle)`
fclose($handle);
?>

Reading a File into an Array with file()

file($filename) reads an entire file and returns it as an array, with each element holding one line -- combining the simplicity of file_get_contents() with the line-by-line structure of fgets(), useful when you want to loop over lines using foreach.

Note: Pass the FILE_IGNORE_NEW_LINES flag to file() if you do not want each array element to include its trailing newline character.

Warning: Like file_get_contents(), file() loads the whole file into memory at once as an array, so it is not ideal for extremely large files.

Example: Reading a File into an Array with file()

php

<?php
// Call `file_put_contents("data.txt", "Line 1\nLine 2\nLine 3")`
file_put_contents("data.txt", "Line 1\nLine 2\nLine 3");
// Declare `$lines`, set to `file("data.txt")`
$lines = file("data.txt");
// Loop over `$lines`, binding each item to `$line`
foreach ($lines as $line) {
    // Print `$line` to the output
    echo $line;
}
?>

Reading a Specific Number of Bytes with fread()

fread($handle, $length) reads up to $length bytes from an open file handle, useful when you need precise control over how much data is read at once -- often paired with filesize() to read an entire binary or text file in one controlled call.

Note: Use fread($handle, filesize($filename)) as a manual alternative to file_get_contents() when you specifically need the open file handle for other operations too.

Warning: Requesting more bytes with fread() than the file actually contains simply reads to the end of the file -- it does not raise an error.

Example: Reading a Specific Number of Bytes with fread()

php

<?php
// Call `file_put_contents("data.txt", "Hello World")`
file_put_contents("data.txt", "Hello World");
// Declare `$handle`, set to `fopen("data.txt", "r")`
$handle = fopen("data.txt", "r");
// Declare `$size`, set to `filesize("data.txt")`
$size = filesize("data.txt");
// Print `fread($handle, $size)` to the output
echo fread($handle, $size);
// Call `fclose($handle)`
fclose($handle);
?>

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