<?php

    // Create an 'anonymous' function without specifying arguments.
    // Arguments are considered to be named $a to $z
    function λ($body)
    {
        $args = '';
        if(preg_match_all('#(\$[a-z])\b#', $body, $matches, PREG_SET_ORDER) !== 0)
        {
            $allArgs = array();
            foreach($matches as $match)
            {
                $allArgs[] = $match[1];
            }
            $allArgs = array_unique($allArgs);
            sort($allArgs);
            $args = implode(',', $allArgs);
        }
       
        // Make sure it's terminated (we don't care about extra trailing ';')
        return create_function($args, $body . ';');
    }
   
   
    // Creating
    $multiply = λ('return $a * $b');
    echo "23 * 65 = " . $multiply(23, 65) . "\n";
   
    // Only $a to $z are reserved
    $bSquaredByA = λ('$unused = "Hello"; $b_square = $b * $b; return $b_square * $a');
    echo "8 * 6^2 = " . $bSquaredByA(8, 6) . "\n";
   
    // Embedding in strings
    $square      = λ('return $a * $a');
    $numbers     = array(2,4,8);
    foreach($numbers as $num)
    {
      echo "$num * $num = {$square($num)}\n";
    }
   
    // Note you don't have to use $a for your first argument, and $b for your second.  They just
    // Need to be in the right order
    $print_two_things = λ('echo "Second: " . $y . "\n"; echo "First: " . $d . "\n";');
    $print_two_things("Hello", "World!");
   
    // Practical use
    $numbers     = array(1,1,1,2,2,3,3,3,4,5,5,6,7,8,9);
    $above_three = array_filter($numbers, λ('return $x > 3;'));
    echo "Numbers above three =  " . implode(", ", $above_three) . "\n";    

?>