The hex2bin() function decodes a hexadecimal string back into raw binary bytes stored in a PHP string. It is the reverse of bin2hex()—not a tool for converting hex numbers to binary notation.
Hex → raw bytes.
Two digits per byte.
Invalid input check.
Encode / decode.
Data vs numbers.
Keys, hashes, dumps.
In PHP, hex2bin() takes a string of hexadecimal characters and returns the original binary data. Each pair of hex digits represents one byte: 48 is the byte for ASCII H, 65 is e, and so on. The result is a normal PHP string holding raw bytes—which may or may not be readable text.
Do not confuse hex2bin() with converting the number 255 to binary digits 11111111. For numeric radix conversion, use base_convert(). Use hex2bin() when you have hex-encoded byte data to decode.
The function accepts one hex-encoded string and returns decoded bytes or false:
string|false hex2bin(string $string)$string — hexadecimal representation of data. Valid characters: 0–9, a–f, A–F. Length must be even.Returns the binary string on success, or false if the input has odd length or contains invalid hex characters. PHP emits an E_WARNING on failure.
hex2bin($hex)Hex → bytes
hex2bin(bin2hex($s))Restore original
$b = hex2bin($hex);
if ($b === false) { ... }Handle failure
base_convert($n, 16, 2)Not hex2bin()
Run these examples in PHP 5.4+. Each demonstrates a common pattern beginners encounter with hex2bin().
Decode a hex string that represents readable ASCII text.
Each pair of hex digits maps to one ASCII character in the decoded output.
<?php
$hexString = "48656c6c6f2c20504850";
$binaryData = hex2bin($hexString);
echo "Hexadecimal: $hexString\n";
echo "Binary: $binaryData\n";
?>48 → H, 65 → e, 6c → l, and so on. The decoded string is plain text because every byte happens to be a printable ASCII character.
Encode with bin2hex(), decode with hex2bin(), and confirm the original is restored.
<?php
$original = "example hex data";
$hex = bin2hex($original);
$restored = hex2bin($hex);
echo "Original: $original\n";
echo "Hex: $hex\n";
echo "Restored: $restored\n";
echo "Match: " . ($original === $restored ? "yes\n" : "no\n");
?>bin2hex() doubles the string length (one byte → two hex chars). hex2bin() reverses that exactly when the hex string is valid.
Error handling, numeric conversion, and non-text byte data.
Always validate the result—invalid hex input fails instead of silently truncating.
<?php
$badHex = "48656c6c6f2"; // 11 chars — odd length
$result = hex2bin($badHex);
echo "Result: " . var_export($result, true) . "\n";
echo "Success: " . ($result !== false ? "yes\n" : "no\n");
?>Each byte needs two hex digits. An odd-length string cannot be decoded completely, so PHP returns false and raises a warning. Always compare with === false.
These functions solve different problems—a common beginner mistake is mixing them up.
<?php
// hex2bin: decode hex-encoded BYTE data
$bytes = hex2bin("ff00"); // 2 raw bytes
echo "hex2bin length: " . strlen($bytes) . "\n";
// base_convert: convert a NUMBER between bases
$digits = base_convert("ff", 16, 2); // "11111111"
echo "base_convert: $digits\n";
?>hex2bin("ff00") produces two binary bytes (255 and 0). base_convert("ff", 16, 2) produces the string "11111111" representing the number 255 in binary notation—completely different semantics.
Not every decoded result is readable text—crypto keys, hashes, and file chunks are often stored as hex.
<?php
$hexKey = "deadbeef01234567";
$bytes = hex2bin($hexKey);
echo "Hex: $hexKey\n";
echo "Byte count: " . strlen($bytes) . "\n";
echo "First byte: " . ord($bytes[0]) . "\n";
echo "Last byte: " . ord($bytes[strlen($bytes) - 1]) . "\n";
?>de → 222, ad → 173, and so on. Use ord() to inspect individual byte values when the decoded string is not human-readable text.
bin2hex() dump to inspect original byte content.hex2bin() WorksInput must contain only valid hex digits with an even character count.
Each pair (e.g. 48) maps to one byte (72). Invalid or odd-length input returns false.
Bytes are concatenated into a PHP string. Length equals half the hex string length.
Ready for crypto, file I/O, or further string processing.
pack('H*', $hex).base_convert() for numeric radix conversion (see Example 4).false with a warning.zz) also return false.false before using the decoded result.The hex2bin() function decodes hex-encoded byte data back into a PHP binary string. Pair it with bin2hex() for encoding, validate return values, and use base_convert() when you need numeric base conversion instead.
Whether you are restoring a debug dump, parsing a protocol field, or loading a crypto key, hex2bin() is the standard PHP tool for hex-to-bytes decoding.
false with strict comparison (=== false)bin2hex() for encode/decode roundtripsbase_convert() for numeric base changesord() and strlen()0x prefixes without stripping themhex2bin()Use these points whenever you decode hex strings in PHP.
Decode byte data.
PurposeTwo digits per byte.
SyntaxOn invalid input.
ErrorsInverse encode.
RelatedData vs numbers.
DistinctionContinue with html_entity_decode(), htmlspecialchars(), and the rest of the string function reference.
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