help with matrix

[super_human]

Hey guys ,
I made a small program that does matrix calculations but seem to be getting an unusual problem:
There are two pages.
matrix.php
[php]

Matrix Tool Matrix A
A₁₁A₁₂A₁₃
A₂₁A₂₂A₂₃
A₃₁A₃₂A₃₃

Matrix B

B₁₁B₁₂B₁₃

B₂₁B₂₂B₂₃

B₃₁B₃₂B₃₃



Operation:

AxB Add Subtract Determenant Of A Determenant Of B [/php]

matrix_core.php
[php]

Answer <?php @$a11 = $_GET['a11']; @$a12 = $_GET['a12']; @$a13 = $_GET['a13']; @$a21 = $_GET['a21']; @$a22 = $_GET['a22']; @$a23 = $_GET['a23']; @$a31 = $_GET['a31']; @$a32 = $_GET['a32']; @$a33 = $_GET['a33'];

@$b11 = $_GET[‘b11’];
@$b12 = $_GET[‘b12’];
@$b13 = $_GET[‘b13’];
@$b21 = $_GET[‘b21’];
@$b22 = $_GET[‘b22’];
@$b23 = $_GET[‘b23’];
@$b31 = $_GET[‘b31’];
@$b32 = $_GET[‘b32’];
@$b33 = $_GET[‘b33’];

@$operation = $_GET[‘operation’];

//Determenant
@$delta1 = $a11*(($a22*$a33)-($a32*$a23));
@$delta2 = $a12*(($a21*$a33)-($a31*$a23));
@$delta3 = $a13*(($a21*$a32)-($a31*$a22));
@$determenant_a = $delta1-$delta2+$delta3;
@$delta4 = $b11*(($b22*$b33)-($b32*$b23));
@$delta5 = $b12*(($b21*$b33)-($b31*$b23));
@$delta6 = $b13*(($b21*$b32)-($b31*$b22));
@$determenant_b = $delta4-$delta5+$delta6;
//Add
@$a1 = $a11+$b11;
@$a2 = $a12+$b12;
@$a3 = $a13+$b13;
@$a4 = $a21+$b21;
@$a5 = $a22+$b22;
@$a6 = $a23+$b23;
@$a7 = $a31+$b31;
@$a8 = $a32+$b32;
@$a9 = $a33+$b33;
//Subtract
@$a10 = $a11-$b11;
@$a11 = $a12-$b12;
@$a12 = $a13-$b13;
@$a13 = $a21-$b21;
@$a14 = $a22-$b22;
@$a15 = $a23-$b23;
@$a16 = $a31-$b31;
@$a17 = $a32-$b32;
@$a18 = $a33-$b33;
//AB
@$row11 = ($a11$b11)+($a12*$b21)+($a13*$b31);
@$row12 = ($a11*$b12)+($a12*$b22)+($a13*$b32);
@$row13 = ($a11*$b13)+($a12*$b23)+($a13*$b33);

@$row21 = ($a21*$b11)+($a22*$b21)+($a23*$b31);
@$row22 = ($a21*$b12)+($a22*$b21)+($a23*$b31);
@$row23 = ($a21*$b13)+($a22*$b23)+($a23*$b33);

@$row31 = ($a31*$b11)+($a32*$b21)+($a33*$b31);
@$row32 = ($a31*$b12)+($a32*$b22)+($a33*$b32);
@$row33 = ($a31*$b13)+($a32*$b23)+($a33*$b33);

if ($operation == ‘Determenant Of A’){
echo "The Determenent of A Matrix is ";
echo $determenant_a.’.’;
}
elseif ($operation == ‘Determenant Of B’){
echo "The Determenent of B Matrix is ";
echo $determenant_b.’.’;
}

elseif ($operation == ‘Add’){
echo 'The answer is: ‘;
echo ‘
’;
echo $a1.’ ‘.$a2.’ ‘.$a3;
echo ‘
’;
echo $a4.’ ‘.$a5.’ ‘.$a6;
echo ‘
’;
echo $a7.’ ‘.$a8.’ '.$a9;
}
elseif ($operation == ‘Subtract’){
echo 'The answer is: ‘;
echo ‘
’;
echo $a10.’ ‘.$a11.’ ‘.$a12;
echo ‘
’;
echo $a13.’ ‘.$a14.’ ‘.$a15;
echo ‘
’;
echo $a16.’ ‘.$a17.’ '.$a18;
}
elseif ($operation == ‘AxB’){
echo 'The answer is: ‘;
echo ‘
’;
echo $row11.’ ‘.$row12.’ ‘.$row13;
echo “
”;
echo $row21.’ ‘.$row22.’ ‘.$row23;
echo “
”;
echo $row31.’ ‘.$row32.’ '.$row33;
}

?>

[/php]

Its all working well ,except for the multiplication part(A*B).
The first 3 numbers are coming as “0 0 0”

Consider an example
Matrix A
3 1 2
4 3 1
2 5 4

Matrix B
3 1 2
4 3 1
2 5 4

The answer is :
17 16 15
26 18 15
34 37 25

But what is displayed when i run the above code is:
0 0 0
26 18 15
34 37 25

I don’t know what i am doing wrong.
Pls Help

[phphelp]

There is logical mistake. Why do you calculate everything each time the form is submitted, if you only need to calculate selected operation? Just do each calculation within the corresponding if block, like this:
[php]if ($operation == ‘Determenant Of A’){
// calculate determenant of A here
// display results here
}
elseif ($operation == ‘Determenant Of B’){
// calculate determenant of B here
// display results here
}
elseif ($operation == ‘Add’){
// calculate sum of 2 matrix here
// display results here
}
// etc.[/php]

In your current code, when you calculate Substruction, you mess all your temporary variables $a11 etc. and then using these modified values when calculating A * B

Also, why don’t you use multi-dimensional arrays? That would simplify output, i.e.:
[php]for($i=1;$i<=3;$i++){
echo $a[1][$i];
}[/php]

[super_human]

i messed up the variables, gave them same names. When i changed the subtraction variables ,it worked perfectly.

Also put the calculations in their respective if blocks.
Thanks for your help