PHP chr() Function

What You’ll Learn

The chr() function converts an integer code point into a single-character string. It is the go-to tool when you know the numeric ASCII value and need the corresponding letter, digit, or symbol—especially in alphabet and pattern programs.

Definition and Usage

In PHP, chr() takes an integer and returns a string containing exactly one character whose code point matches that number. For example, chr(65) returns "A" because 65 is the ASCII code for uppercase A. It is the opposite of ord(), which converts a character back to its numeric code.

📝 Syntax

The chr() function accepts one integer parameter:

string chr(int $codepoint)

Parameters

• $codepoint — an integer representing the desired character code. Common ASCII range: 0–127. Extended bytes: 128–255. Unicode code points are supported in PHP 7.1+.

Return Value

Returns a string containing a single character. If the code point is invalid, PHP 8.0+ throws a ValueError.

Examples Gallery

Run these examples in any PHP 7+ environment. Each one demonstrates a common pattern beginners encounter with chr().

<?php
$asciiCode = 65;
$character = chr($asciiCode);

echo "ASCII code: $asciiCode\n";
echo "Character:  $character\n";
?>

ASCII code: 65
Character:  A

<?php
$codes = [65, 90, 97, 122, 48, 57, 33];

foreach ($codes as $code) {
    echo "$code => '" . chr($code) . "'\n";
}
?>

65 => 'A'
90 => 'Z'
97 => 'a'
122 => 'z'
48 => '0'
57 => '9'
33 => '!'

<?php
$letter = "M";
$code   = ord($letter);
$back   = chr($code);

echo "Letter:    $letter\n";
echo "ord():     $code\n";
echo "chr():     $back\n";
echo "Match:     " . ($back === $letter ? "yes\n" : "no\n");
?>

Letter:    M
ord():     77
chr():     M
Match:     yes

<?php
echo "Uppercase: ";
for ($i = 65; $i <= 90; $i++) {
    echo chr($i);
}
echo "\n";

echo "Lowercase: ";
for ($i = 97; $i <= 122; $i++) {
    echo chr($i);
}
echo "\n";
?>

Uppercase: ABCDEFGHIJKLMNOPQRSTUVWXYZ
Lowercase: abcdefghijklmnopqrstuvwxyz

<?php
$newline = chr(10);  // LF (line feed)
$tab     = chr(9);   // horizontal tab

echo "Line 1" . $newline;
echo $tab . "Indented line\n";

echo "ord(newline) = " . ord($newline) . "\n";
echo "ord(tab)     = " . ord($tab) . "\n";
?>

Line 1
	Indented line
ord(newline) = 10
ord(tab)     = 9

🚀 Common Use Cases

• Alphabet and star patterns — generate A–Z dynamically inside nested loops.
• Building strings from codes — construct characters when you only have numeric data.
• Protocol and binary work — produce specific byte values for low-level formats.
• Encoding exercises — pair with ord() to teach ASCII fundamentals.
• Legacy code reading — understand programs that build text from integer tables.

📝 Notes

• Standard ASCII covers codes 0–127. Extended ASCII uses 128–255.
• ord() is the inverse: chr(ord($c)) === $c for single-byte characters.
• For multi-byte UTF-8 text, prefer mb_chr() from the mbstring extension.
• PHP 8.0+ throws ValueError for code points outside 0–1114111 (0x10FFFF).
• In most tutorials, chr(64 + $i) where $i is 1–26 produces A–Z.

💡 Best Practices