BenGoldberg

Still have figured this out, and I only have one more day. Anyone?

Eval seems to be the right function for my application, but for the life of me I can not get it to work. Here's the basic code I'm working with. <form action="<?php echo $_SERVER['PHP_SELF']; ?>" method="post"> <table> <tr> <td>Enter function y prime:</td> <td><input type="text" size="50" maxlength="" name="yprime" value="<?php echo (isset($_POST['yprime']) ? $_POST['yprime'] : '')?>" /></td> </tr> </table> </br> <input type="submit" name="rk" value="Submit" /> </form> <?php $yprime = strval( $_POST['yprime'] ); //saving the function as a string function dydx($x,$y){ eval("\$equation = \"$yprime\";"); return $equation; } echo dydx(3,2); //equals 0 when it should equal 9 (yprime being 3*$x) ?> (The example input i use for yprime is 3*$x) I've done hours of googling and researching how eval works, but no matter what I try, the function dydx() always returns 0. The code above is what I believe to be my best attempt at getting it to evaluate $yprime properly, but it doesn't work. Argh!

WOW I'm not sure why I forgot to try this. You would think it would work, and it does keep the values in the forms, which I wanted to do anyways. But I just tested it and as soon as I hit that second submit button it still wipes out all my old data. Now I really don't know why, but I guess I don't fully understand how the SELF POST method works. Any other ideas? And thank you btw for helping me with this, it's actually part of a school project that's due Thursday so it really is a big help.

One more question. So I have a function with two parameters, $x and $y. Here it is. function dydx($x,$y){ $equation = 2 * $x; return $equation; } Now here's the problem. I want $equation to be user defined. Easy enough, I use a post command and I get $equation to equal whatever the user inputs. The problem is that if I get input from the user, I'm not sure how to take that input and then have the function parameters work on it. Like if the user inputs "3*$x + 2*$y", i want to be able to let the parameters for the function dydx act on it. How could I go about doing this?

Ok so here's what I have now... <form action="<?php echo $_SERVER['PHP_SELF']; ?>" method="post"> <table> <tr> <td>Enter function y prime:</td> <td><input type="text" size="50" maxlength="" name="yprime" value="" /></td> </tr> <tr> <td>Enter number of partitions:</td> <td><input type="text" size="7" maxlength="7" name="partitions" value="" /></td> </tr> <tr> <td>Enter initial x value, x(0):</td> <td><input type="text" size="3" maxlength="3" name="initialx" value="" /></td> </tr> <tr> <td>Enter the ending x value:</td> <td><input type="text" size="3" maxlength="3" name="endingx" value="" /></td> </tr> <tr> <td>Enter initial y value, y(0):</td> <td><input type="text" size="3" maxlength="3" name="initialy" value="" /></td> </tr> </table> </br> <input type="submit" name="runge kutta name" value="Run Program" /> </form> <?php if ($_SERVER['REQUEST_METHOD'] == 'POST' ) { // make sure that the form is posted $yprime = $_POST['yprime']; $partitions = $_POST['partitions']; $initialx = $_POST['initialx']; $endingx = $_POST['endingx']; $initialy = $_POST['initialy']; function dydx($x,$y){ $equation = 2 * $x; return $equation; } if ($_POST['partitions'] != 0) { $h = ($endingx - $initialx)/$partitions; } $a[1] = $initialx; $b[1] = $initialy; for ($i = 1; $i <= $partitions; $i++) { $k1 = dydx($a[$i], $b[$i]); $k2 = dydx($a[$i] + (1/2)*$h, $b[$i] + (1/2)*$h*$k1); $k3 = dydx($a[$i] + (1/2)*$h, $b[$i] + (1/2)*$h*$k2); $k4 = dydx($a[$i] + $h, $b[$i] + $h*$k3); $a[$i + 1] = $a[$i] + $h; $b[$i + 1] = $b[$i] + (1/6)*$h*($k1 + 2*$k2 + 2*$k3 + $k4); } for ($i = 1; $i <= $partitions + 1; $i++) { $xyarray["$a[$i]"] = $b[$i]; } $_SESSION['graph'] = $xyarray; } // if ($_SERVER['REQUEST_METHOD'] == 'POST' ) ends ?> </br></br> Choose a partition of X: <form action="<?php echo $_SERVER['PHP_SELF']; ?>" method="post"> <select name="output"> <?php for ($i = 1; $i <= $partitions + 1; $i++) { echo "<option value=\"$b[$i]\">$a[$i]</option>\n"; } ?> </select> <input type="submit" name="runge kutta name" value="See Y" /> </form> <?php echo $_POST['output']; I put in my second post command to display the y value for the corresponding x value, and it almost works. It successfully displays the value I expect it to but it wipes out all the data from the $a and $b arrays at the same time. I would like to preserve that data until new data is inputted for partitions, initial x, ending x, and initial y. This is where I'm having problems.

Alright, here's the important stuff. Don't get too caught up in the math, the important thing to know is my $a array are my x values and my $b array are my y values. I created the drop down menu of the x values at the end but there is no attempt on there of trying to display the y values. But basically if they choose $a[37] I would like $b[37] to be displayed. <form action="<?php echo $_SERVER['PHP_SELF']; ?>" method="post"> <?php function dydx($x,$y){ $equation = 3 * pow($x, 2); return $equation; } ?> <table> <tr> <td>Enter number of partitions:</td> <td><input type="text" size="7" maxlength="7" name="partitions" value="" /></td> </tr> <tr> <td>Enter initial x value, x(0):</td> <td><input type="text" size="3" maxlength="3" name="initialx" value="" /></td> </tr> <tr> <td>Enter the ending x value:</td> <td><input type="text" size="3" maxlength="3" name="endingx" value="" /></td> </tr> <tr> <td>Enter initial y value, y(0):</td> <td><input type="text" size="3" maxlength="3" name="initialy" value="" /></td> </tr> </table> </br> <input type="submit" name="runge kutta name" value="Run Program" /> </form> <?php $partitions = $_POST['partitions']; $initialx = $_POST['initialx']; $endingx = $_POST['endingx']; $initialy = $_POST['initialy']; if ($_POST['partitions'] != 0) { $h = ($endingx - $initialx)/$partitions; } $a[1] = $initialx; $b[1] = $initialy; for ($i = 1; $i <= $partitions; $i++) { $k1 = dydx($a[$i], $b[$i]); $k2 = dydx($a[$i] + (1/2)*$h, $b[$i] + (1/2)*$h*$k1); $k3 = dydx($a[$i] + (1/2)*$h, $b[$i] + (1/2)*$h*$k2); $k4 = dydx($a[$i] + $h, $b[$i] + $h*$k3); $a[$i + 1] = $a[$i] + $h; $b[$i + 1] = $b[$i] + (1/6)*$h*($k1 + 2*$k2 + 2*$k3 + $k4); } for ($i = 1; $i <= $partitions + 1; $i++) { $xyarray["$a[$i]"] = $b[$i]; } $_SESSION['graph'] = $xyarray; ?> </br></br> Choose a partition of X: <select name="output"> <?php for ($i = 1; $i <= $partitions + 1; $i++) { echo "<option value=\"$a[$i]\">$a[$i]</option>\n"; } ?>

So basically I'm using PHP to solve a math problem for me. The user puts in a few parameters and the program runs those numbers through the algorithm and spits out a bunch of xy coordinates. I'm using the PHP SELF method to retrieve the user input. This all works fine, but it's afterwords that I run into problems. I create a drop down menu of all the x values and I want the user to be able to choose any x value they wish and to have the corresponding y value be displayed. The problem is that I have to use another POST command for this and when I do, it wipes out all the computed data. Of course the y-value is never displayed, and there lies the problem. I'm sure there are many ways to get around this, but I could not find one out myself. Anyone have any ideas?

Ah yes, perfect. Thanks everyone!

Thanks you guys, it works just how I expect it to! The only thing is, is it possible to not copy the quotation marks? I just want the data inside them.

I entered in a valid string with quotation marks, but I'm just getting an empty array for $matches. I guess it's not matching anything. ???

I'm really horrible with regex but I need to use it for a site that I'm building, so that's why I'm here. Basically, I need to extract data between two quotation marks and store the value in a variable. An example of a string that I need to work on is... deg_F = "---.-" But I need to do this for quite a few lines. The cool thing is for every one, the data is inside the quotation marks. Another example... percent = "--" So the quotation marks don't always start at the same point since the strings are different, but the data I need is always inside the quotation marks. Any help would be greatly appreciated!

Ah yes, I see now. Duh. Well I knew it was something silly like that.

Holy moly! Thank you so much, works perfectly now. Can I ask why this fixes the problem though? Why does $records[0] not count the values correctly? It seems like count($records) and count($records[0]) would output the same number no matter what. In any case, I can move on with my website now, so thanks again!

Well it's displaying a lot, but here's the first two arrays it displays... array(3) { [0]=> array(3) { [0]=> string(3) "106" [1]=> string(11) "08 15, 2008" [2]=> string(1) "1" } [1]=> array(3) { [0]=> string(3) "106" [1]=> string(11) "08 14, 2008" [2]=> string(1) "2" } [2]=> array(3) { [0]=> string(3) "108" [1]=> string(11) "08 14, 2008" [2]=> string(1) "3" } } array(1) { [0]=> array(3) { [0]=> string(3) "107" [1]=> string(11) "08 15, 2008" [2]=> string(1) "1" } } It then has 6 undefined offsets and then more arrays and errors... The values that var_dump are displaying are the ones I expected. Does this help?

Hi, I have a script that compares integers and ranks them from lowest to highest, and then submits those rankings to a mysql table. If two or more integers are the same, I have it so they're ranked the same and the next integer is ranked where it would appear if there was no tie, example... $a = 1 $b = 1 $c = 2 $a and $b would be ranked 1st because they're tied for the lowest value while $c would be ranked third, not second. Anyways, I created a relatively simple function to do this and in testing, it's outputting the values I expected it to. The only thing is that it's giving me undefined offset errors, but I don' see why. Here's the function... <?php /* FUNCTION TO ENTER RANKINGS INTO DATABASE */ function post_rankings() { $result = mysql_query("SELECT * FROM auf_records") or die(mysql_error()); $u = 17; $x = 18; $y = 19; while ($u < mysql_num_fields($result)) { /* RETRIEVE DATA FROM TABLE "AUF_RECORDS" */ $level = mysql_field_name($result, $u); $date = mysql_field_name($result, $x); $recrank = mysql_field_name($result, $y); $result2 = mysql_query("SELECT $level, $date, id FROM auf_records") or die(mysql_error()); while ($row = mysql_fetch_row($result2)) { if ($row[0] > 0) { $records[] = $row; } } if (isset($records)) { sort($records); $i = 0; $numrec = count($records[0]); while ($i < $numrec) { $uid = $records[$i][2]; // FIRST UNDEFINED OFFSET if ($i == 0) { $rank = $i + 1; mysql_query("UPDATE auf_records SET $recrank = '$rank' WHERE id = '$uid' ") or die(mysql_error()); } else { $a = $i - 1; if ($records[$i][0] == $records[$a][0]) { // SECONDS UNDEFINED OFFSET $prevuid = $records[$a][2]; // THIRD UNDEFINED OFFSET $result3 = mysql_query("SELECT $recrank FROM auf_records WHERE id = '$prevuid' ") or die(mysql_error()); $row2 = mysql_fetch_row($result3); $rank = $row2[0]; mysql_query("UPDATE auf_records SET $recrank = '$rank' WHERE id = '$uid' ") or die(mysql_error()); } else { $rank = $i + 1; mysql_query("UPDATE auf_records SET $recrank = '$rank' WHERE id = '$uid' ") or die(mysql_error()); } } $i++; } } $u = $u + 3; $x = $x + 3; $y = $y + 3; unset($records); } } ?> I'm getting Undefined offset: 1 for all three undefined offsets but only Undefined offset: 2 for the first two undefined offsets. If $records isn't set if (isset($records)) should take care of that, so why am I getting this error. I'm sure it's something simple, but I can't find it by myself. Any help would be greatly appreciated!