Help! Empty PHP Variables from a MySQL query

egasker

Hello, I am pulling my last strand of hair out! Can you help?

I have a BASIC php script that successfully reads in a field containing HTML code. I can echo the field and PHP displays the HTML without problems. But! When I add <?=time()?> or any other PHP function or variable into the same field, PHP returns nothing. Here's the example:
<?
.....yadda connection strings, etc.

//Simple query returns data from one field successfully
$precode_query = "SELECT element_precode FROM elements WHERE pages_id = '$pos' AND subpages_id = '$spos'";

$precode_query_result = mysql_query($precode_query);

$table = mysql_fetch_row($precode_query_result);

//echo works fine until it interprets a <? & ?> tag within the $table array, then nothing appears.. no variables show up and no functions like time() work
echo $table[0];

Now here's the weird part -- element_precode will return its field contents without problem if it's text or HTML data. However, if I add in ANY PHP, it returns nothing, and no errors. Here's what a WORKING element_precode field would look like when echoed:

<table><tr><td>Hey there, this works fine.</td></tr></table>

But if I change the field contents to look like below, it returns only "Time:"

Does anyone know how to read in field contents and have PHP interpret the contents?

Thanks,
Evan

[deleted]

Well, what makes you think hat printing time() should make PHP execute time() as a function? You're not executing anything are you, you're just printing.

If you want to exute the string, you must run it through eval(), but I advise trongly against putting executable data in a database.

[deleted]

"I understand what you mean by trying to execute a function when I am printing it. How does this work with variables? Do I have to eval() variables as well in order to get the printed string to parse the PHP as desired?"

Yes.

The data inside a database is just plain ASCII, and when you print that with PHP then PHP will obviously not execute it.

The reason why you do NOT want to do this is because 'eval()' executes the code asif the code was pasted into the source at the place where eval() was called.

So any functions or vars you reference are pulled from the script that does the eval().

So if you do:

eval('<? exit;?>');

then you script will exit.

and if you have a loop like:

while $iT<100

and you eval:

eval('<? $iT=100; ?>')

then the loop stops because $iT has reached 100.

egasker

Thanks Vincente, the eval function is exactly what I needed.

For those of you who want to pull HTML and PHP code from a database field, it is important to note the following:

When you use mysql_fetch_row (or any other fetch method), you'll need to strip the slashes if you have those automatically inserted into your table data, and you also will need to prepend a PHP close tag before reading in the field data. The following (updated) code solved my original problem:

<?
.....yadda connection strings, etc.

//Simple query returns data from one field successfully
$precode_query = "SELECT element_precode FROM elements WHERE pages_id = '$pos' AND subpages_id = '$spos'";

$precode_query_result = mysql_query($precode_query);

$table = mysql_fetch_row($precode_query_result);

eval(stripslashes('?>'.$table[0]));

All this works great for functions, but NOT for variables, by the way! If you want to have PHP evaluate a variable within a database field, you need to make sure your headers have the values declared before the table is queried. Otherwise, when you eval() a field containing a PHP variable, your output will be null!

To get around this, simply use the ob_start() and ob_end_flush() function (and be sure that your ISP or your php.ini has output buffering set to "On"):

ob_start();
$variable = "Anything you want to declare";
$variable2 = "And so on...";
ob_end_flush();

Now everything between ob_start and ob_end_flush is sent to the header before the PHP page renders. When you display the database field that references $variable2, your output will now display "And so on..."

Here's what my database field looks like using a function:

<? echo "<table width=100%><tr><td>Time:".time()."</td></tr></table>"; ?>

That's how the field should appear. You can also do the same for variables:

<? echo "<table width=100%><tr><td>Time:$time_to_var</td></tr></table>"; ?>

I'm embarrased to say how much time this took to figure out. Let me know if this is useful to you!