PHP chunk_split() Function – Complete Guide with Examples

What is chunk_split() in PHP?

The chunk_split() function in PHP splits a string into smaller chunks and inserts a separator (default is a newline \r\n).

📌 Use cases:

  • Formatting long strings for readability.
  • Breaking text into fixed-length parts (e.g., Base64 encoding).
  • Generating output-friendly formatted text.

Syntax of chunk_split()

string chunk_split(string $string, int $length = 76, string $separator = "\r\n")

🔹 Parameters:

  1. $string → The input string.
  2. $length → (Optional) The chunk size (default = 76 characters).
  3. $separator → (Optional) String inserted after each chunk (default = "\r\n").

🔹 Return Value:

  • Returns the formatted string with chunks separated by the given separator.

Example: Splitting a String into Chunks

<?php
$text = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
$chunked_text = chunk_split($text, 5, "-");

echo $chunked_text;
?>

✅ Output:

ABCDE- FGHIJ- KLMNO- PQRST- UVWXY- Z-

📌 How it works?

  • The input string "ABCDEFGHIJKLMNOPQRSTUVWXYZ" is split into chunks of 5 characters.
  • A hyphen (-) is added after each chunk.

Example: Splitting a Base64-Encoded String

<?php
$data = base64_encode("Hello, PHP chunk_split!");
$formatted = chunk_split($data, 4, " ");

echo $formatted;
?>

✅ Output:

SGVs IG8s IFBI UCBj dW5r X3Nw bGl0 ISE=

📌 Why use chunk_split() here?

  • Base64-encoded data often needs fixed-length formatting for readability.

Example: Formatting Credit Card Numbers

<?php
$card_number = "1234567812345678";
$formatted = chunk_split($card_number, 4, " ");

echo $formatted;
?>

✅ Output:

1234 5678 1234 5678

📌 Why use chunk_split() here?

  • It formats credit card numbers for better readability.

Handling Edge Cases

🔹 What happens if the length exceeds the string size?

<?php
$text = "Hello";
echo chunk_split($text, 10, "-");
?>

✅ Output:

Hello-

🔹 What if the separator is an empty string?

<?php
$text = "HelloWorld";
echo chunk_split($text, 3, "");
?>

✅ Output:

Hel loW orl d

📌 Best practice: Always specify a meaningful separator to avoid unexpected formatting.

Best Practices for Using chunk_split()

✅ 1. Use for Readability

  • Use chunk_split() for breaking long text into readable parts (e.g., Base64, credit cards).

✅ 2. Handle Edge Cases

  • If the string is shorter than $length, chunk_split() adds a separator at the end.

✅ 3. Avoid Unnecessary Use

  • If you need an array of chunks, consider str_split() instead:

 

<?php
print_r(str_split("HelloWorld", 3));
?>
✅ Output:
Array ( [0] => Hel [1] => loW [2] => orl [3] => d )

📌 Use str_split() when you need an array instead of a formatted string.

When to Use chunk_split()

📌 Use chunk_split() when:
✅ You need formatted output (e.g., Base64 encoding, credit card numbers).
✅ You want to insert separators after a fixed number of characters.

⚠️ Avoid if:
❌ You need an array instead – use str_split().
❌ The formatting doesn’t require separators.