wp_rand() WP 2.6.2

Generates a random number between the specified min and max.

This is a pluggable function, and it can be replaced by a plugin. It means that this function is defined (works) only after all plugins are loaded (included), but before this moment this function has not defined. Therefore, you cannot call this and all functions depended on this function directly from a plugin code. They need to be called on plugins_loaded hook or later, for example on init hook.

Function replacement (override) — in a plugin you can create a function with the same name, then it replace this function.

Is the basis for: wp_generate_password()

✈ 1 time = 0.000032s = very fast | 50000 times = 0.09s = speed of light | PHP 7.0.8, WP 4.6.1

No Hooks.

Return

Int. A random number between min and max

Usage

wp_rand( $min, $max );

$min(int): Lower limit for the generated number
Default: 0
$max(int): Upper limit for the generated number
Default: 0

Examples

#1 Basic usage

echo wp_rand( 99, 99999 ); // 19899, 85724, 77130, 51575
echo wp_rand( 1.5, 5.5 );  // 5, 1, 3, 4
echo wp_rand( 5, 4 );      // always 5

Notes

Global. String. $rnd_value
Static. String. $seed
Static. true/false. $use_random_int_functionality

Changelog

Since 2.6.2	Introduced.
Since 4.4.0	Uses PHP7 random_int() or the random_compat library if available.

Code of wp rand: `wp-includes/pluggable.php` ^{WP 5.4.2}

<?php
function wp_rand( $min = 0, $max = 0 ) {
	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

	// 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 {
			$_max = ( 0 != $max ) ? $max : $max_random_number;
			// 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.
	if ( 0 != $max ) {
		$value = $min + ( $max - $min + 1 ) * $value / ( $max_random_number + 1 );
	}

	return abs( intval( $value ) );
}

Related Functions

From tag: PHP analogues (PHP functions replacement)

wp_sprintf()