Print a list of common divisors given two integers.

common_divisors.php

<?php

// Print a list of common divisors given two integers.
function generate($min, $max) {
    // Base case: max >= min > 1
    if ($min <= 1 || $min > $max) {
        return;
    }
    // A divisor if, max modulo min has 0 remainder, print it.  
    echo $max % $min == 0 ? " $min " : '';
  
    return 1 * generate($min + 1, $max);
}

// Inputs
$array = [[1,5], [2, 6], [5, 7], [5, 24], [3, 10], [7,27]];
foreach ($array as $mm) {
    $min = $mm[0];
    $max = $mm[1];
    echo "($min, $max)\n";
    generate($min, $max);  
    echo "\n\n";
}

// stdout
// (1, 5)


// (2, 6)
//  2  3  6 

// (5, 7)
//  7 

// (5, 24)
//  6  8  12  24 

// (3, 10)
//  5  10 

// (7, 27)
//  9  27