PHP hexdec() Function

The hexdec() function converts a hexadecimal string to its decimal equivalent. This function is useful when working with color codes, memory addresses, or any data represented in hexadecimal format.

Syntax

hexdec(string $hex_string): int|float

Parameters

Return Value

Returns the decimal representation as an integer or float. Large values may return as float due to integer overflow.

Examples

Basic Hexadecimal Conversion

Converting common hexadecimal values to decimal ?

<?php
    echo "hexdec('A') = " . hexdec('A') . "<br>";
    echo "hexdec('FF') = " . hexdec('FF') . "<br>";
    echo "hexdec('1A') = " . hexdec('1A') . "<br>";
    echo "hexdec('0x1A') = " . hexdec('0x1A') . "<br>";
?>

hexdec('A') = 10
hexdec('FF') = 255
hexdec('1A') = 26
hexdec('0x1A') = 26

Color Code Conversion

Converting HTML color codes to decimal values ?

<?php
    $color = 'FF5733';
    $red = hexdec(substr($color, 0, 2));
    $green = hexdec(substr($color, 2, 2));
    $blue = hexdec(substr($color, 4, 2));
    
    echo "Color #$color:<br>";
    echo "Red: $red<br>";
    echo "Green: $green<br>";
    echo "Blue: $blue<br>";
?>

Color #FF5733:
Red: 255
Green: 87
Blue: 51

Large Values and Edge Cases

Demonstrating behavior with large numbers and invalid input ?

<?php
    echo "hexdec('FFFFFFFF') = " . hexdec('FFFFFFFF') . "<br>";
    echo "hexdec('G') = " . hexdec('G') . "<br>";
    echo "hexdec('') = " . hexdec('') . "<br>";
?>

hexdec('FFFFFFFF') = 4294967295
hexdec('G') = 0
hexdec('') = 0

Key Points

? Case insensitive − 'ff' and 'FF' produce the same result
? Invalid characters are ignored and conversion stops at first invalid character
? Empty strings or strings with no valid hex characters return 0
? Optional '0x' prefix is supported

Conclusion

The hexdec() function provides a simple way to convert hexadecimal strings to decimal numbers. It's particularly useful for color manipulation, binary data processing, and working with memory addresses in PHP applications.