max() / min() / rand() / random_int() Since: PHP 4（2000）

// Returns the maximum value. Accepts an array or multiple values as arguments.
max($value1, $value2, ...);

// Returns the minimum value. Accepts an array or multiple values as arguments.
min($value1, $value2, ...);

// Generates a pseudo-random number.
rand($min, $max);

// Generates a pseudo-random number using the Mersenne Twister algorithm.
mt_rand($min, $max);

// Generates a cryptographically secure random integer.
random_int($min, $max);

max() and min() return the largest or smallest value among the arguments, preserving the original type. All random number functions return an integer within the specified range. random_int() throws an exception if generation fails.

<?php
// Get the maximum value using max().
echo max(10, 25, 3); // Outputs '25'.
echo max(-5, -1, -10); // Outputs '-1'.

// Get the maximum and minimum values from an array.
$scores = [85, 92, 78, 96, 88];
echo max($scores); // Outputs '96'.
echo min($scores); // Outputs '78'.

// Practical example: use min() to enforce a lower bound.
$quantity = -3;
$safe_quantity = max(0, $quantity); // Clamps the negative value to 0, outputs '0'.
echo $safe_quantity;

// Practical example: clamp a value within a range.
$page = 150;
$page = max(1, min($page, 100)); // Clamps to the range 1–100, outputs '100'.
echo $page;

// Generate a pseudo-random number using rand().
echo rand(1, 6); // Outputs a random integer between 1 and 6.

// Generate a pseudo-random number using the Mersenne Twister algorithm.
echo mt_rand(1, 100); // Outputs a random integer between 1 and 100.

// Generate a cryptographically secure random number using random_int().
echo random_int(100000, 999999); // Outputs a secure 6-digit random number.

// Practical example: generate a secure token.
$token = random_int(0, PHP_INT_MAX);
echo $token; // Outputs an unpredictable random integer.

max() and min() find the extreme values from an array or multiple arguments. They are commonly used to enforce upper and lower bounds — for example, max(0, $value) clamps a value to zero or above, and max(1, min($value, 100)) restricts a value to a specific range.

rand() and mt_rand() are not suitable for security-sensitive use. When generating values that must be unpredictable — such as password reset tokens or CSRF tokens — always use random_int(). It uses the operating system's cryptographically secure random number generator, making its output computationally infeasible to predict.

For generating random strings, random_bytes() can be used to work with raw byte sequences. For rounding numbers, see round() / ceil() / floor().