[Resolved] Obtaining the value of a variable whose name is created on the fly.

[showman]

Hi,

I'm having a problem doing something that I know I used to do (a long time ago)

I think it is referred to as variable variables.

What needs to happen is that a variable name is dynamically generated in the script, and I need to get the value of that variable name.

I have various arrays set up with the variable names keyed on the track number they are following.

Here is the test that I am running and not getting what I need

//assign the array values
$x2=array(1 => 2,3,37.5,0);  

//define the track being followed
$track=2;
//dynamically create the variable name
$show='$x'.$track.'[1]';
//Display the results to verify 
print"show is $show<br>value of show is ".$$show."<br>";

The results I get are
show is $x2[1]
value of show is

and what I expected to get is
show is $x2[1]
value of show is 2

I have tried numerous variations on what should be a simple script, but can't seem to get it to do what I think it should.

Could someone straighten me out, or at least head me in the right direction? Or am I just way off base?

If what I'm asking doesn't make sense, please someone let me know so I can clarify.. This is extremely important at this point, and I could really use some assistance.

Thanks in advance.

doug

[Installer]

FWIW, this will work:

$x2 = array(1 => 2, 3, 37.5, 0);   

$track = 2; 
$show = 'x' . $track . '[1]';
echo 'show is $' . $show . '<br>';
$show = eval('return $' . $show . ';'); 
echo 'value of show is ' . $show . '<br>';

[Drakla]

This is a little reminder to myself whenever I guff up variable variable things

<pre>
<?php
	for ($i = 1; $i < 5; $i++)
	{
		${'r' . $i} = $i * 10 . ' chahhh';			// $r1, $r2 etc
		${'X' . $i*10} = $i * 10 . ' zing!';		// $X10, $X20 DOESN'T NEED BRACKETS
		${'Y' . ($i + 500)} = $i + 500 . ' Noo Noo';// $Y500, $Y501 NEED BRACKETS

	$r{$i} = $i * 100 . ' mooolooo';			// acts as $r[$i]
}

$vars = get_defined_vars();
	// take out any key with underscores
foreach ($vars as $key => $value)
	if (strpos($key, '_') !== false)
		unset($vars[$key]);

ksort($vars);
print_r($vars);
?>
</pre>
<?php
	echo 'THIS FILE:';
	highlight_file($_SERVER['SCRIPT_FILENAME']) or die(' NO HIGHTLING CODE');
?>

But I don't think you can use indexes in variable names, so Installer's way is probably bang-on if you want to use them.

[showman]

Thank you Installer and Drakla for your responses..

While I'm not sure if I understand Drakla's coding and functionality, I'm going to keep it around to study and see if I can make use of it.

The info that Installer sent was dead on, and did exactly what I needed it to do..

thank you again.

Doug

[Installer]

I glad it helped.

You probably noticed that my code really doesn't do any variable variable stuff, but just appears to (although v-vs may be constructed internally somewhat in this way). The line "$show = 'x' . $track . '[1]';" constructs the string, and the next line merely echos it. The line after that just returns the value of the string treated as code, and the last line echoes that value.

So while "$show" will retain the value for later use, if the value of "$x2[1]" is changed, the value of "$show" won't be.

Why your posted code didn't work, in short: 1) "$", "[", and "]" are illegal characters in variable names; 2) "[n]" isn't part of a variable name, but an offset "parameter".

Have a happy 4th. 🙂