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Request #24274 New 'function' variable_exists(); patch included
Submitted: 2003-06-20 17:08 UTC Modified: 2014-12-30 10:41 UTC
Votes:2
Avg. Score:5.0 ± 0.0
Reproduced:1 of 1 (100.0%)
Same Version:0 (0.0%)
Same OS:0 (0.0%)
From: torben@php.net Assigned:
Status: No Feedback Package: *General Issues
PHP Version: * OS: Any
Private report: No CVE-ID: None
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 [2003-06-20 17:08 UTC] torben@php.net
Description:
------------
PHP doesn't have a way to check whether a variable exists; just a way to check whether it has a value (isset()). This isn't wrong, but it would be useful to add a way to check for actual existence of a variable (for instance, checking for array keys without having to go through array_key_exists()).

Here's a patch against CVS which implements variable_exists(). The only difference to isset() is that a variable is considered to exist even if it contains NULL.


Index: zend_compile.h
===================================================================
RCS file: /repository/Zend/zend_compile.h,v
retrieving revision 1.145
diff -u -r1.145 zend_compile.h
--- zend_compile.h	31 Dec 2002 15:55:02 -0000	1.145
+++ zend_compile.h	20 Jun 2003 11:35:20 -0000
@@ -558,6 +558,7 @@
 
 #define ZEND_ISSET				(1<<0)
 #define ZEND_ISEMPTY			(1<<1)
+#define ZEND_VARIABLE_EXISTS    (1<<2)
 
 #define ZEND_CT	(1<<0)
 #define ZEND_RT (1<<1)
Index: zend_execute.c
===================================================================
RCS file: /repository/Zend/zend_execute.c,v
retrieving revision 1.321
diff -u -r1.321 zend_execute.c
--- zend_execute.c	31 Dec 2002 15:55:02 -0000	1.321
+++ zend_execute.c	20 Jun 2003 11:35:22 -0000
@@ -2382,7 +2382,7 @@
 								isset = 1;
 							}
 						}
-					} else if (*var==EG(uninitialized_zval_ptr) || ((*var)->type == IS_NULL)) {
+ 					} else if (*var == EG(uninitialized_zval_ptr) || (((*var)->type == IS_NULL) && EX(opline)->op2.u.constant.value.lval != ZEND_VARIABLE_EXISTS)) { 
 						value = *var;
 						isset = 0;
 					} else {
@@ -2391,6 +2391,7 @@
 					}
 
 					switch (EX(opline)->op2.u.constant.value.lval) {
+						case ZEND_VARIABLE_EXISTS:
 						case ZEND_ISSET:
 							EX(Ts)[EX(opline)->result.u.var].tmp_var.value.lval = isset;
 							break;
Index: zend_language_parser.y
===================================================================
RCS file: /repository/Zend/zend_language_parser.y,v
retrieving revision 1.23
diff -u -r1.23 zend_language_parser.y
--- zend_language_parser.y	4 Aug 2002 06:39:44 -0000	1.23
+++ zend_language_parser.y	20 Jun 2003 11:35:22 -0000
@@ -112,6 +112,7 @@
 %token T_UNSET
 %token T_ISSET
 %token T_EMPTY
+%token T_VARIABLE_EXISTS
 %token T_CLASS
 %token T_EXTENDS
 %token T_OBJECT_OPERATOR
@@ -710,6 +711,7 @@
 
 internal_functions_in_yacc:
 		T_ISSET '(' isset_variables ')' { $$ = $3; }
+	|	T_VARIABLE_EXISTS '(' variable_exists_variables ')' { $$ = $3; }
 	|	T_EMPTY '(' cvar ')'	{ zend_do_isset_or_isempty(ZEND_ISEMPTY, &$$, &$3 TSRMLS_CC); }
 	|	T_INCLUDE expr 			{ zend_do_include_or_eval(ZEND_INCLUDE, &$$, &$2 TSRMLS_CC); }
 	|	T_INCLUDE_ONCE expr 	{ zend_do_include_or_eval(ZEND_INCLUDE_ONCE, &$$, &$2 TSRMLS_CC); }
@@ -717,6 +719,11 @@
 	|	T_REQUIRE expr			{ zend_do_include_or_eval(ZEND_REQUIRE, &$$, &$2 TSRMLS_CC); }
 	|	T_REQUIRE_ONCE expr		{ zend_do_include_or_eval(ZEND_REQUIRE_ONCE, &$$, &$2 TSRMLS_CC); }
 ;
+
+variable_exists_variables:
+		cvar 							{ zend_do_isset_or_isempty(ZEND_VARIABLE_EXISTS, &$$, &$1 TSRMLS_CC); }
+	|	variable_exists_variables ',' 	{ zend_do_boolean_and_begin(&$1, &$2 TSRMLS_CC); } cvar { znode tmp; zend_do_isset_or_isempty(ZEND_ISSET, &tmp, &$4 TSRMLS_CC); zend_do_boolean_and_end(&$$, &$1, &tmp, &$2 TSRMLS_CC); }
+;	
 
 isset_variables:
 		cvar 				{ zend_do_isset_or_isempty(ZEND_ISSET, &$$, &$1 TSRMLS_CC); }
Index: zend_language_scanner.l
===================================================================
RCS file: /repository/Zend/zend_language_scanner.l,v
retrieving revision 1.64
diff -u -r1.64 zend_language_scanner.l
--- zend_language_scanner.l	13 Feb 2003 16:46:16 -0000	1.64
+++ zend_language_scanner.l	20 Jun 2003 11:35:23 -0000
@@ -927,6 +927,10 @@
 	return T_ISSET;
 }
 
+<ST_IN_SCRIPTING>"variable_exists" {
+	return T_VARIABLE_EXISTS;
+}
+
 <ST_IN_SCRIPTING>"empty" {
 	return T_EMPTY;
 }


Reproduce code:
---------------
<?php
error_reporting(E_ALL);
ini_set('display_errors', true);

echo "<h3>Array testing</h3>";
echo "\$arr = array(1 => null, 2 => array(1 => 3, 2 => null));\n\n";
$arr = array(1 => null, 2 => array(1 => 3, 2 => null));
echo "variable_exists(\$arr[1]): " . (variable_exists($arr[1]) ? 'yes' : 'no') . " (should be yes)\n";
echo "variable_exists(\$arr[2]): " . (variable_exists($arr[2]) ? 'yes' : 'no') . " (should be yes)\n";
echo "variable_exists(\$arr[3]): " . (variable_exists($arr[3]) ? 'yes' : 'no') . " (should be no)\n";
echo "variable_exists(\$arr[1][2]): " . (variable_exists($arr[1][2]) ? 'yes' : 'no') . " (should be no)\n";
echo "variable_exists(\$arr[2][1]): " . (variable_exists($arr[2][1]) ? 'yes' : 'no') . " (should be yes)\n";
echo "variable_exists(\$arr[2][2]): " . (variable_exists($arr[2][2]) ? 'yes' : 'no') . " (should be yes)\n";
echo "variable_exists(\$arr[2][3]): " . (variable_exists($arr[2][3]) ? 'yes' : 'no') . " (should be no)\n";

echo "<h3>Scalar testing</h3>";
echo "\$foo = null\n\n";
$foo = null;
echo "variable_exists(\$foo): " . (variable_exists($foo) ? 'yes' : 'no') . " (should be yes)\n";
echo "unset(\$foo);\n";
unset($foo);
echo "variable_exists(\$foo): " . (variable_exists($foo) ? 'yes' : 'no') . " (should be no)\n";
echo "variable_exists(\$bar): " . (variable_exists($bar) ? 'yes' : 'no') . " (should be no)\n";
?>

Actual result:
--------------
(Actual output from PHP 4.3.2 with the given patch):

Array testing
$arr = array(1 => null, 2 => array(1 => 3, 2 => null));

variable_exists($arr[1]): yes (should be yes)
variable_exists($arr[2]): yes (should be yes)
variable_exists($arr[3]): no (should be no)
variable_exists($arr[1][2]): no (should be no)
variable_exists($arr[2][1]): yes (should be yes)
variable_exists($arr[2][2]): yes (should be yes)
variable_exists($arr[2][3]): no (should be no)
Scalar testing
$foo = null

variable_exists($foo): yes (should be yes)
unset($foo);
variable_exists($foo): no (should be no)
variable_exists($bar): no (should be no)


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 [2003-06-20 17:28 UTC] torben at thebuttlesschaps dot com
Hmm. A non-messed-up patch can be found here:

 http://www.thebuttlesschaps.com/variable_exists_patch.txt


Torben
 [2003-06-22 10:10 UTC] cunha17 at uol dot com dot br <Cristiano Duarte>
I think it is a nice function. Are there any plans to commit it to CVS ?
 [2003-08-22 12:06 UTC] xuefer at 21cn dot com
we have isset() and empty()
not variable_isset() nor variable_isempty()
so why variable_exists() ? why not just exists() ?
it will be widely used if it's implemented
so keep it short if possible :)
 [2012-05-18 14:03 UTC] mark at unserver dot de
Any news on this? The current solution (using array_key_exists on $GLOBALS) is quite ugly.
 [2014-04-16 18:37 UTC] levim@php.net
-Status: Open +Status: Feedback -Package: Feature/Change Request +Package: *General Issues -Operating System: All +Operating System: Any -PHP Version: 4CVS-2003-06-20 (stable) +PHP Version: *
 [2014-04-16 18:37 UTC] levim@php.net
What value is knowing if a variable exists? In the local scope you should already know what variables exist. The only other use cases I can think of are checking array keys or object properties and there are already functions for those. What are your current thoughts?
 [2014-12-30 10:41 UTC] php-bugs at lists dot php dot net
No feedback was provided. The bug is being suspended because
we assume that you are no longer experiencing the problem.
If this is not the case and you are able to provide the
information that was requested earlier, please do so and
change the status of the bug back to "Re-Opened". Thank you.
 
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