Basic Matrix Operations Script

Adrianz

Hello my fellow PHP coders out there

I have been working on a Matrix Operations PHP script and I am having trouble with my verification of data input from the form I cannot see where my logic has gone wrong. My main problem is that if I hit the "Resize" button with no data the solved_matrices.php script has junk info i.e no tables just headings. This also happens with no input data. I think I might need to use a combination of isset() and empty() functions. Am I on the right track?Also another question. Can input data get "mixed" up if you use both the GET and POST methods when passing data through a form.
Here is a snippet of my code: (Hope that I am clear!)

If anyone has any doubt I have attached the files...

solved_matrices.php

<html>

<head>
	<title>Solved Matrix Operations</title>
</head>

<body bgcolor="#000000" text="#FFFFFF">
<center><h3><u><a name="Top_Page">Results for Basic Matrix Operations</a></u></h3></center>
<?

$matrixA = $_POST["matrix_A"];
$matrixB = $_POST["matrix_B"];
$num_rows_A = $_POST["number_rows_A"];
$num_cols_A = $_POST["number_cols_A"];
$num_rows_B = $_POST["number_rows_B"];
$num_cols_B = $_POST["number_cols_B"];
$constant_A = $_POST["const_A"];
$constant_B = $_POST["const_B"];

// Check each of the matrices if they contain non numeric data
$chk1 = check_matrices($num_rows_A, $num_cols_A, $matrixA);
$chk2 = check_matrices($num_rows_B, $num_cols_B, $matrixB);

if (!($chk1 && $chk2)) {
echo "<center><b>ERROR: You did not input any values<br><a href=\"matrices.php\">Back to the main page</a></b></center>";
} else {
//solve/evaluate the matrices

function check_matrices($rows, $cols, $matrix) {
	for ($i = 0; $i < $rows; $i++) {
		for ($j = 0; $j < $cols; $j++) {
			$elem = $matrix[$i][$j];
			if (!is_numeric($elem) || ($elem == "")) {
				//exit();
				//echo "<a href=\"matrices.php\">Back to the main page</a>";
				return(0);
			}
		}
	}
	return(1);
}

Cheers
Adrian

halojoy

function check_matrices($rows, $cols, $matrix) {

suppose $rows=0;

in this case will be NO LOOP

for( $i = 0; $i < $rows; ......
i = 0, and to loop is required $i < $rows;

Is 0 less than 0 ... NO!
In this case function will return return (1) ... true

You have written a function, where the exception from (1) is tested.
And the true state is set a normal return.
Maybe you should try the other, oposite approach.

======================================

Sometimes, if not most times, is better to CHECK for SCORE.

Take a game of normal European Football.
We have 1 judge, to decide if is GOAAAALLL, or not.

In a game of footbal normal result is like 2-1.
Many attempts will fail to make goal. Shots will not even come near Goal-Keeper.

Best method for judge(s) here is:
- nothing is goal

- until can be proven be a goal

Test goal.
1. set $result = false
2. has ball crossed line between goal sticks? if so then $result=true
3. return $result

=========================

Test if I was paid or not. (a bad method)
1. set $result= true
2. Test all ways and cases NOT TO PAY ME. if such case $result=false
3. return $result

Test if I was paid or not. (correct better method)
1. set $result= false
2. Did I get the money. if such case $result=true
3. return $result

regars 🙂
halojoy