<?php

/**
 * Simple php equivalent of Oracle's coalesce()
 *
 * It can be used as simple oneline-alternative to switch or if operators in many
 * cases without difficult logic. For example, get first non-empty value from bunch of vars:
 *
 * echo coalesce($var1, $var2, $var3, ...);
 *
 * is alternative to:
 *
 * if ($var1) {
 *     return $var1;
 * } elseif ($var2) {
 *     return $var2;
 * } elseif ....
 *
 * or
 *
 * return $var1 ?? $var2 ?? $var3 ...
 *
 * @see https://docs.oracle.com/cd/B28359_01/server.111/b28286/functions023.htm
 * @author Anthony Axenov
 * @return mixed|null
 */
function coalesce() {
    foreach (func_get_args() as $arg) {
        if (is_callable($arg)) {
            $arg = call_user_func($arg);
        }
        if ($arg !== null) {
            return $arg;
        }
    }
    return null;
}

//usage:

$var1 = null;
$var2 = function() use ($var1) {
    return $var1;
};
$var3 = 3;
$var4 = '4';

$result = coalesce($var1, $var2, $var3, $var4);
var_dump($result);