Generates a random non-negative number.

$min int Optional

Lower limit for the generated number.
Accepts positive integers or zero. Defaults to 0.

Default: null

$max int Optional

Upper limit for the generated number.
Accepts positive integers. Defaults to 4294967295.

Default: null

int A random non-negative number between min and max.

File: wp-includes/pluggable.php. View all references

function wp_rand( $min = null, $max = null ) {
	global $rnd_value;

	// Some misconfigured 32-bit environments (Entropy PHP, for example)
	// truncate integers larger than PHP_INT_MAX to PHP_INT_MAX rather than overflowing them to floats.
	$max_random_number = 3000000000 === 2147483647 ? (float) '4294967295' : 4294967295; // 4294967295 = 0xffffffff

	if ( null === $min ) {
		$min = 0;
	}

	if ( null === $max ) {
		$max = $max_random_number;
	}

	// We only handle ints, floats are truncated to their integer value.
	$min = (int) $min;
	$max = (int) $max;

	// Use PHP's CSPRNG, or a compatible method.
	static $use_random_int_functionality = true;
	if ( $use_random_int_functionality ) {
		try {
			// wp_rand() can accept arguments in either order, PHP cannot.
			$_max = max( $min, $max );
			$_min = min( $min, $max );
			$val  = random_int( $_min, $_max );
			if ( false !== $val ) {
				return absint( $val );
			} else {
				$use_random_int_functionality = false;
			}
		} catch ( Error $e ) {
			$use_random_int_functionality = false;
		} catch ( Exception $e ) {
			$use_random_int_functionality = false;
		}
	}

	// Reset $rnd_value after 14 uses.
	// 32 (md5) + 40 (sha1) + 40 (sha1) / 8 = 14 random numbers from $rnd_value.
	if ( strlen( $rnd_value ) < 8 ) {
		if ( defined( 'WP_SETUP_CONFIG' ) ) {
			static $seed = '';
		} else {
			$seed = get_transient( 'random_seed' );
		}
		$rnd_value  = md5( uniqid( microtime() . mt_rand(), true ) . $seed );
		$rnd_value .= sha1( $rnd_value );
		$rnd_value .= sha1( $rnd_value . $seed );
		$seed       = md5( $seed . $rnd_value );
		if ( ! defined( 'WP_SETUP_CONFIG' ) && ! defined( 'WP_INSTALLING' ) ) {
			set_transient( 'random_seed', $seed );
		}
	}

	// Take the first 8 digits for our value.
	$value = substr( $rnd_value, 0, 8 );

	// Strip the first eight, leaving the remainder for the next call to wp_rand().
	$rnd_value = substr( $rnd_value, 8 );

	$value = abs( hexdec( $value ) );

	// Reduce the value to be within the min - max range.
	$value = $min + ( $max - $min + 1 ) * $value / ( $max_random_number + 1 );

	return abs( (int) $value );
}