Codility-lesson3-TapeEquilibrium.php

<?php
// you can write to stdout for debugging purposes, e.g.
// print "this is a debug message\n";

// difference |(A[0] + A[1] + ... + A[P − 1]) − (A[P] + A[P + 1] + ... + A[N − 1])|

function solution($A) {
    // write your code in PHP5.5
    $n = count($A);

    $minimal_diference = null;
    $sufix = $A;
    $prefix = array();
    array_push($prefix, $sufix[0]);
    array_shift($sufix);
    $sum_prefix = array_sum($prefix);
    $sum_sufix = array_sum($sufix);
    $minimal_diference = abs($sum_sufix - $sum_prefix);

    for($i = 1; $i < $n; $i++)
    {
        $difference = abs($sum_sufix - $sum_prefix);
        //print_r($difference);
        if ($difference < $minimal_diference) {
            $minimal_diference = $difference;
        }

        if ($minimal_diference == 1) return $minimal_diference;

        //$cur_value = current($sufix);
        //array_shift($sufix);
        $cur_value = $sufix[$i-1];
        $sum_prefix += $cur_value;
        $sum_sufix -= $cur_value;
    }

    return $minimal_diference;
}