<?php
	error_reporting(E_ALL ^ E_NOTICE);

	class Polynomial {
		private $coefficients = array();
		private $debug = false;

		function __construct($inputArr) {
			$loop = 0;
			foreach($inputArr AS $thisPart) {
				// It was ignoring 0 values, hense using a loop counter to insert values
				$this->coefficients[$loop] = $thisPart;
				$loop++;
			}

			print_r($this->coefficients);
		}

		function getVal($integer) {
			# Run it, return a value

			for($i = 0; $i < count($this->coefficients); $i++) {
				if($i == 0) {
					// x^0
					$outVal[] = $this->coefficients[$i];
				} elseif ($i == 1) {
				// x^1
					$outVal[] = ($this->coefficients[$i] * $integer);
				} else {
					//x^2 x^3 x^4
					$outVal[] = ($this->coefficients[$i] * $this->raisePower($integer, $i));
				}
			}

				if($this->debug) {
					print_r($outVal);
				}

				foreach($outVal AS $val) {
					$sum = $sum + $val;
				}

			return $sum;
		}

		// take a value, raise it to a power
		function raisePower($baseNumber, $power) {
			$loop = 1;

			if($power == 0) {
				return 1;
			} else {
				while($loop != $power) {
					if($loop == 1) {
						$integer = $baseNumber * $baseNumber;
					} else {
						$integer = $baseNumber * $integer;
					}

					$loop++;
				}
			}

			if($this->debug) {
				echo "Raising $baseNumber to the power of $power and got a result of $integer <br />";
			}
			return $integer;
		}

		// debug
		function debug($bool) {
			$this->debug = $bool;
		}

		function gdebug() {
			return $this->debug;
		}

	}

	set_time_limit(0);

	/* Input function values */
	//$input = array(1,2,3,4);
	$input = array(2,-7,8,0,-1);
	//$input = array(-2,2,-3,3);

	/* Initialise a Poly object with $input */
	$thisPoly = new Polynomial($input);

	/*
	 * Find two values that lie on polynomial
	 * Probably a better way to do this
	 */

	# Generate < 0
	$attempts = 0;
	do {
		$thisNo = rand(-5000, 5000);

		if($attempts > 20000) {
			break;
		}

		# Feed into function
		$val[0] = $thisPoly->getVal($thisNo);
		$took[0]++;

		$attempts++;

		if($val[0] == 0) {
			continue;
		}
	} while ($val[0] > 0);

	# Generate > 0

	$attempts = 0;
	do {
		# Just a theory ... Will only work for a small amount of polynomials
		$thisNo = rand(-5000, 5000);

		if($attempts > 20000) {
			break;
		}

		# Feed into function
		$val[1] = $thisPoly->getVal($thisNo);
		$took[1]++;

		$attempts++;
	} while ($val[1] < 0);

	$a = $val[0];
	$b = $val[1];
	$tol = 0.000000000000001;
	$limitLoop = 10000;

	echo "Starting Values <br><br>";
	echo "A is $a<br>";
	echo "B is $b<br>";

	$n = 1;
	while($n < $limitLoop) {
		$c = (($a + $b) / 2);

		if($thisPoly->gdebug()) {
			//echo "Poly of c = " . $thisPoly->getVal($c) . " and tol setting is " . (($b - $a) / 2) . "<br />";
		}

		if(($thisPoly->getVal($c) == 0) || (($b - $a) / 2) < $tol) {
			// sol found
			echo "Solution: " . $c;
			break;
		} else {
			$n++;

			if((($thisPoly->getVal($c) < 0) && ($thisPoly->getVal($a) < 0)) || (($thisPoly->getVal($c) > 0) && ($thisPoly->getVal($a) > 0))) {
				$a = $c;
			} else {
				$b = $c;
			}
		}
	}

?>