The dechex() function in PHP is used to convert a decimal (base 10) number into its hexadecimal (base 16) representation. This function is useful in various applications, such as color manipulation, low-level programming, and network programming, where hexadecimal notation is commonly used.

Syntax:

dechex(int $number): string

• $number: The decimal number to be converted. This must be an integer.
• Return Value: Returns the hexadecimal representation of the given decimal number as a string. The result will be in lowercase letters.

Example 1: Basic Usage

<?php
echo dechex(255);
?>

Output:

ff

Explanation: The decimal number 255 is converted to its hexadecimal equivalent, which is ff.

Example 2: Conversion of Larger Numbers

<?php
echo dechex(4095);
?>

Output:

fff

Explanation: The decimal number 4095 is represented in hexadecimal as fff.

Example 3: Negative Numbers

<?php
echo dechex(-15);
?>

Output:

fffffffffffffff1

Explanation: When a negative number is provided, PHP converts it to its two's complement hexadecimal representation. Here, -15 is represented as fffffffffffffff1 in a 64-bit format.

Example 4: Zero

<?php
echo dechex(0);
?>

Output:

0

Explanation: The hexadecimal representation of 0 is simply 0.

Key Points:

• Input Type: The input for dechex() must be an integer. If a non-integer value is provided, it will be converted to an integer.
• Negative Numbers: The function does not throw an error for negative numbers; instead, it returns their two's complement representation in hexadecimal format.
• Output Format: The output is in lowercase. If uppercase letters are desired, you can use the strtoupper() function to convert the result.

Example of Practical Use:

<?php
$decimalNumber = 345;
$hexadecimalRepresentation = dechex($decimalNumber);
echo "The hexadecimal representation of $decimalNumber is: $hexadecimalRepresentation\n";

// Example of using in color representation
$red = 255;
$green = 0;
$blue = 128;
$hexColor = dechex($red) . dechex($green) . dechex($blue);
echo "Hexadecimal color representation: #$hexColor\n";
?>

Output:

The hexadecimal representation of 345 is: 159
Hexadecimal color representation: #ff0080

Explanation: In this example, dechex() is used to convert a decimal number to its hexadecimal representation and to create a hexadecimal color code from RGB values.

In summary, dechex() is a useful PHP function for converting decimal numbers into hexadecimal format, making it essential for applications that involve hexadecimal notation, such as color codes and low-level data manipulation.