php match variable names using wildcard - php

Question

I need to check for the existence of a variable.
Variables are not necessarily created in order 1.2.3. They could be created 2.4.3.1. These are also not created at the same time on the same page. So I am just wanted to check for the existence of the variable.
$_SESSION['rule1']
$_SESSION['rule2']
$_SESSION['rule3']
$_SESSION['rule4']
<?
if(isset($_SESSION['rule'.*wildcard*'])) {
do something
}
?>
I'm not sure how to go about this. The answer probably lies in REGEX but I am horrible with REGEX.

Answer 1

If you don't know need to know which rule* key is in the session array, only if any of them are present, then you could try this:
<?php
function prefixExists(array $assoc_array, $prefix)
{
$length = strlen($prefix);
foreach ($assoc_array as $key => $unused)
{
if (strncmp($key, $prefix, $length) === 0) {
return true;
}
}
return false;
}
Testing as follows:
session_start();
var_dump(prefixExists($_SESSION, 'rule'));
$_SESSION['rule3'] = 'some value from form';
var_dump(prefixExists($_SESSION, 'rule'));
Gives output:
bool(false)
bool(true)

Answer 2

Here is another solution with the use of preg_match:
function arrayHasSimilarKey(array $array, $matchKey)
{
$pattern = '/' . str_replace('*', '.*', $matchKey) . '/i';
foreach ($array as $key => $value) { echo $key.PHP_EOL;
if (preg_match($pattern, $key)) {
return true;
}
}
return false;
}
$testArray = ['abc' => 1, 'test_1' => 1, 'test_2' => 1, 'test2_1' => 1, 'test3_2' => 1];
$tests = [
0 => arrayHasSimilarKey($testArray, 'test*'), // true
1 => arrayHasSimilarKey($testArray, 'test2*_2'), // false
2 => arrayHasSimilarKey($testArray, 'test3*'), // true
3 => arrayHasSimilarKey($testArray, 'test3*_1'), // false
4 => arrayHasSimilarKey($testArray, '*_2') // false
];
var_dump($tests);
In your case, $testArray would be $_SESSION