Functions to currying and compose functions with PHP.

functional_programming_compose.php

<?php
// This function allows creating a new function from two functions passed into it		
//e.g.:		
//php > $explode = curry_left("explode", ",");		
//php > $toUpper = curry_left("strtoupper");		
//php > $map = curry_left("array_map", $toUpper);		
//php > $compose = compose($map, $explode);		
//php > print_r($compose("paulo,ricardo,koch"));		
//Array		
//(		
//    [0] => PAULO		
//    [1] => RICARDO		
//    [2] => KOCH		
//)		
function compose(&$f, &$g) 		
{		
  // Return the composed function		
  return function() use ($f, $g) {		
    // Get the arguments passed into the new function		
    $x = func_get_args();		
    // Call the function to be composed with the arguments		
    // and pass the result into the first function.		
    return $f(call_user_func_array($g, $x));		
  };		
}

functional_programming_curry_left.php

<?php

//This function allows creating a new function that needs the last parameter of other function
//e.g.:
//php > $func = curry_left("explode", ",");
//php > print_r( $func("paulo,koch"));
//Array
//(
//    [0] => paulo
//    [1] => koch
//)
function curry_left($callable)
{
    $outer_arguments = func_get_args();
    array_shift($outer_arguments);
 
    return function() use ($callable, $outer_arguments) {
        return call_user_func_array($callable, array_merge($outer_arguments, func_get_args()));
    };
}

functional_programming_curry_right.php

<?php
//This function allows creating a new function that needs the first parameter of other function		
//e.g.:		
//php > $func = curry_right("strpos", ",");		
//php > print_r( $func("paulo,koch") );		
//5		
function curry_right($callable)		
{		
    $outer_arguments = func_get_args();		
    array_shift($outer_arguments);		
 		
    return function() use ($callable, $outer_arguments) {		
        return call_user_func_array($callable, array_merge(func_get_args(), $outer_arguments));		
    };		
}