Re: Re: variable_exists() patch

On Thu, 2003-08-14 at 08:42, Andi Gutmans wrote: > I am not really convinced either that variable_exists() is > function_exists() parallel. > Under what circumstances is this needed? > > Andi The followup I sent to Ilia gives examples of how this patch can be used to determine whether, for instance, array keys exist, without having to use the array_key_exists() workaround; also, you can check whether an object has defined an attribute, even if it hasn't yet assigned it a value: <?php class foo { var $bar; var $baz = null; var $quux = 'quux'; } $foo = new foo; echo "variable_exists(\$foo-&gt;bar): " . (variable_exists($foo->bar) ? 'yes' : 'no') . " (should be yes)\n"; echo "variable_exists(\$foo-&gt;baz): " . (variable_exists($foo->baz) ? 'yes' : 'no') . " (should be yes)\n"; echo "variable_exists(\$foo-&gt;quux): " . (variable_exists($foo->quux) ? 'yes' : 'no') . " (should be yes)\n"; echo "variable_exists(\$foo-&gt;quuux): " . (variable_exists($foo->quuux) ? 'yes' : 'no') . " (should be no)\n"; echo "isset(\$foo-&gt;bar): " . (isset($foo->bar) ? 'yes' : 'no') . " (should be yes)\n"; echo "isset(\$foo-&gt;baz): " . (isset($foo->baz) ? 'yes' : 'no') . " (should be yes)\n"; echo "isset(\$foo-&gt;quux): " . (isset($foo->quux) ? 'yes' : 'no') . " (should be yes)\n"; echo "isset(\$foo-&gt;quuux): " . (isset($foo->quuux) ? 'yes' : 'no') . " (should be no)\n"; ?> ...the output from the above is: ----------------------------------------------------------------------- variable_exists($foo->bar): yes (should be yes) variable_exists($foo->baz): yes (should be yes) variable_exists($foo->quux): yes (should be yes) variable_exists($foo->quuux): no (should be no) isset($foo->bar): no (should be yes) isset($foo->baz): no (should be yes) isset($foo->quux): yes (should be yes) isset($foo->quuux): no (should be no) ----------------------------------------------------------------------- etc. It's a little annoying at times that that isset() doesn't do what its name suggests it should, which leads people to try to use it for things which is seems that it should be able to do, but can't. When I've tried to explain it, the only answer I can give is "Sorry, that's just the way it is--and no, you can't do that in PHP". It seems basic enough functionality that is almost, but not quite, satisfied by isset(). -- Torben Wilson <torben@php.net> +1.604.709.0506 http://www.thebuttlesschaps.com http://www.inflatableeye.com http://www.hybrid17.com http://www.themainonmain.com -----==== Boycott Starbucks! http://www.haidabuckscafe.com ====-----