php - in a foreach loop how to determine if the current key has a value set?

In an associative array in a foreach loop, I want to skip key -value pairs that have no value set. How can I do this? I tried like below, and similar using isset() but it still adds the keys with empty values to the string.

foreach ($_POST as $param_name => $param_val) {   
    if (
        !empty($param_val) 
        && $param_name !== 'Last_Name' 
        && $param_name !== 'First_Name' 
        && $param_name !== 'Middle_Name'  
        && $param_name !== 'Country' 
        && $param_name !== 'Locality' 
        && $param_name !== 'Fathers_Name' 
        && $param_name !== 'Mothers_Name' 
        && $param_name !== 'Birthdate'
    ) {
        $classname = $param_name;
        $pagestring = $pagestring."<h2>$param_name</h2><span id='$param_name' name='$param_name' class='$classname textstyle'>$param_val</span>";
    } else {
        $tags[] = $param_val;
        $classname = $param_name."style"; $pagestring = $pagestring."<h2>$param_name</h2><div id='$param_name' name='$param_name' class='$classname textstyle'>$param_val</div>";
    }

I do not want $param_name => $param_val pairs that don't have a value posted to get added to $pagestring

Solution:

You can use array_filter (https://www.php.net/manual/en/function.array-filter.php):

<?php

$arr = ['First_name' => 'foo', 'Last_name' => 'bar', 'empty_value' => ''];

print_r(array_filter($arr));

Output:

Array
(
    [First_name] => foo
    [Last_name] => bar
)

It will remove also false, null and 0.

If you want to keep zeroes, use

array_filter($arr, 'strlen');