<?php

$size = $_GET['size'];

$i = 0;

$prnum = true;

while ( $i < $size && $prnum )

{

$j = 0;

while ( $j < $size && $prnum )

{

$pointer = 'el_' . $i .$j;

// check entered data on numeric value

if ( is_numeric ($matrix[$i][$j] = $_POST[$pointer]) ) {

// $matrix1 is a copy of the $matrix

$matrix1[$i][$j] = $matrix[$i][$j];

$inverse_matrix[$i][$j] = 0;

$one[$i][$j] = 0;

// addition to left side of the $matrix the unit matrix

$matrix[$i][$j + $size] = 0;

$j++;

} else {

/* the value entered into a matrix cell not numerical*/

write_to_errors_file

('Error : The value = '. $matrix[$i][$j] . ' entered into the matrix cell -' . $i . $j .

'- is not numerical.' . "</br>");

$prnum = false;

}

}

$matrix[$i][$i+$size] = 1;

$i++;

}

// inverse matrix finding

// determinant matrix calculation

if ( $prnum ) {

//reduction of a matrix to a triangular look

$b = 0;

$sch = 0;// counter of transfer of lines

$i = 0;

$pr = true;

do {

if ($matrix[$i][$i] != 0) {

for ($j = $i + 1; $j < $size; $j++) {

$b = $matrix[$j][$i] / $matrix[$i][$i];

for ($k = 0; $k < 2 * $size; $k++) {

$matrix[$j][$k] = $matrix[$j][$k] - $matrix[$i][$k] * $b;

}

}

$i++;

} else {

$l = 1; // line exchange

do {

$sch = $sch + 1;

for ($j = $i; $j < 2 * $size; $j++) {

$b = $matrix [$i][$j];

$matrix [$i][$j] = $matrix [$i + $l][$j];

$matrix [$i + $l][$j] = $b;

}

$l++;

if ($l > $size - $i - 1) {

write_to_errors_file('Matrix determinant equals to 0.' . "</br>" .

'Inverse matrix could not be found.' . "</br>");

$pr = false;

}

} while ($matrix [$i][$i] == 0 && $pr);

}

} while ($i < $size && $pr);

if ($pr) {

$det = 1;

for ($i = 0; $i < $size; $i++) {

$det = $det * $matrix [$i][$i];

}

$det = $det * st($sch);

// calculation of elements of the inverse matrix

// $c = 0;

for ($i = 0; $i < $size; $i++) {

for ($j = $size - 1; $j > -1; $j--) {

$c = 0;

for ($k = 0; $k < $size; $k++) {

$c = $c + $matrix [$j][$k] * $inverse_matrix [$k][$i];

}

$b = 1 / $matrix [$j][$j];

$inverse_matrix [$j][$i] = round($b * ($matrix [$j][$i + $size] - $c), 6);

}

}

foreach ($inverse_matrix as $i => $line) {

foreach ($line as $j => $el) {

$inverse_matrix[$i][$j] = round($el * $det, 2);

}

}

//Multiplication of an initial matrix by the inverse matrix

for ($i = 0; $i < $size; $i++) {

for ($j = 0; $j < $size; $j++) {

$c = 0;

$matrix2 [$i][$j] = round($det * $matrix [$i][$j], 6);

for ($k = 0; $k < $size; $k++) {

$c = $c + $matrix1[$i][$k] * $inverse_matrix [$k][$j];

}

$one [$i][$j] = round($c, 6);

}

}

foreach ($one as $i => $line) {

foreach ($line as $j => $el) {

$one[$i][$j] = round($el / $det, 2);

}

}

require __DIR__ . '/views/inverse_matrix_output.php';

require __DIR__ . '/views/output.php';

output('Matrix Inversion service'. "</br>");

output('The initial matrix =' . "</br>");

matrix_output($matrix1, $size);

output('The initial matrix determinant = ' . $det . "</br>");

output('The inverse matrix = 1/(' . $det . ') * ' . "</br>");

matrix_output($inverse_matrix, $size);

output('The result of multiplication of the initial matrix by the inverse matrix' . "</br>");

matrix_output($one, $size);

require_once __DIR__ . '/modules/matrix_file_write.php';

$path = __DIR__ . '/matrix_safe.php';

//putting up of the $matrix1 in storage matrix_safe.php

matrix_write($matrix1, $path);

$path = __DIR__ . '/inverse_matrix_safe.php';

//putting up of the $inverse matrix in storage inverse_matrix_safe.php

matrix_write($inverse_matrix, $path);

$path = __DIR__ . '/matrix_determinant_safe.php';

//putting up of the matrix determinant in storage matrix_determinant_safe.php

error_write_file($det, $path);

}

}

require_once __DIR__ . '/modules/matrix_file_write.php';

$path = __DIR__ . '/errors.php';

$errors = error_read_file($path);

if ( isset($errors[0]) ) {

foreach ($errors as $el)

{

echo "</br>";

echo $el;

}

$errors = [];

error_write_file($errors,$path);

}

?>

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<?php

// (-1) in degree n

function st($n) {

}

function write_to_errors_file($str)

}