PHP bin2hex() Function

What You’ll Learn

The bin2hex() function converts a string of raw bytes into a hexadecimal text representation. Each byte becomes two hex digits—ideal for displaying hashes, debugging binary data, or storing non-text bytes in a readable format.

Definition and Usage

In PHP, strings are binary-safe—they can hold any sequence of bytes, not just readable text. bin2hex() takes such a string and returns a hexadecimal encoding where every byte is written as two characters. For example, the text "Hello, PHP!" becomes 48656c6c6f2c2050485021.

📝 Syntax

The bin2hex() function accepts one string parameter:

string bin2hex(string $string)

Parameters

• $string — the binary data to encode. In PHP, ordinary strings already hold raw bytes, so text like "ABC" works perfectly.

Return Value

Returns a lowercase hexadecimal string. The output length is always twice the input byte length. The original string is not modified.

Examples Gallery

Run these examples in any PHP 7+ environment. Each one demonstrates a common pattern beginners encounter with bin2hex().

<?php
$binaryData = "Hello, PHP!";
$hexString  = bin2hex($binaryData);

echo "Binary Data: $binaryData\n";
echo "Hex String:  $hexString\n";
echo "Input length:  " . strlen($binaryData) . " bytes\n";
echo "Output length: " . strlen($hexString) . " chars\n";
?>

Binary Data: Hello, PHP!
Hex String:  48656c6c6f2c2050485021
Input length:  11 bytes
Output length: 22 chars

<?php
$bytes = "\x00\x0A\xFF\x41";  // NUL, newline, 255, 'A'
$hex   = bin2hex($bytes);

echo "Hex: $hex\n";
?>

Hex: 000aff41

<?php
$original = "CodeToFun";
$hex      = bin2hex($original);
$restored = hex2bin($hex);

echo "Original: $original\n";
echo "Hex:      $hex\n";
echo "Restored: $restored\n";
echo "Match:    " . ($restored === $original ? "yes\n" : "no\n");
?>

Original: CodeToFun
Hex:      436f6465546f46756e
Restored: CodeToFun
Match:    yes

<?php
$password = "mySecret123";

// hash() with true returns raw 20-byte SHA-1 binary
$rawHash = hash("sha1", $password, true);
$hexHash = bin2hex($rawHash);

// hash() without true already returns hex — compare lengths
$directHex = hash("sha1", $password);

echo "Raw hash length:  " . strlen($rawHash) . " bytes\n";
echo "bin2hex output:   $hexHash\n";
echo "hash() default:   $directHex\n";
echo "Same result:      " . ($hexHash === $directHex ? "yes\n" : "no\n");
?>

Raw hash length:  20 bytes
bin2hex output:   ac640ea4eceea98eab494069d0fc7f1d1b4f8a5c
hash() default:   ac640ea4eceea98eab494069d0fc7f1d1b4f8a5c
Same result:      yes

<?php
$number = 255;
$text   = "\xFF";  // single byte with value 255

echo "dechex(255):     " . dechex($number) . "\n";
echo "bin2hex(\"\\xFF\"): " . bin2hex($text) . "\n";
echo "bin2hex(\"255\"):   " . bin2hex("255") . "\n";
?>

dechex(255):     ff
bin2hex("\xFF"): ff
bin2hex("255"):   323535

🚀 Common Use Cases

• Hash and checksum display — show SHA, MD5, or HMAC digests as readable hex strings.
• Debugging binary data — inspect file contents, network packets, or API responses byte by byte.
• UUID and token formatting — convert raw binary identifiers to hex for logs or URLs.
• Data serialization — store binary blobs in text-only formats like JSON or CSV.
• Learning encoding — understand how bytes map to hexadecimal before exploring Base64 or other encodings.

📝 Notes

• Output is always lowercase. Use strtoupper() if you need uppercase hex.
• Output length = 2 × input byte length. A 16-byte UUID raw string produces 32 hex characters.
• hex2bin() reverses the process but returns false on invalid input.
• For large files, consider reading in chunks rather than loading entire files into memory before encoding.
• bin2hex() is encoding, not encryption—hex strings can be decoded by anyone.

💡 Best Practices