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                                     unset

   (PHP 3, PHP 4 )
   unset -- Unset a given variable

Description

   void unset ( mixed var [, mixed var [, ...]])

   unset() destroys the specified variables. Note that in PHP 3, unset()
   will always return TRUE (actually, the integer value 1). In PHP 4,
   however, unset() is no longer a true function: it is now a statement.
   As such no value is returned, and attempting to take the value of
   unset() results in a parse error.

   Example 1. unset() example
   <?php
   // destroy a single variable
   unset($foo);
   // destroy a single element of an array
   unset($bar['quux']);
   // destroy more than one variable
   unset($foo1, $foo2, $foo3);
   ?>

   The behavior of unset() inside of a function can vary depending on
   what type of variable you are attempting to destroy.

   If a globalized variable is unset() inside of a function, only the
   local variable is destroyed. The variable in the calling environment
   will retain the same value as before unset() was called.

   <?php
   function destroy_foo() {
       global $foo;
       unset($foo);
   }
   $foo = 'bar';
   destroy_foo();
   echo $foo;
   ?>

   The above example would output:

   bar

   If a variable that is PASSED BY REFERENCE is unset() inside of a
   function, only the local variable is destroyed. The variable in the
   calling environment will retain the same value as before unset() was
   called.

   <?php
   function foo(&$bar) {
       unset($bar);
       $bar = "blah";
   }
   $bar = 'something';
   echo "$bar\n";
   foo($bar);
   echo "$bar\n";
   ?>

   The above example would output:

something
something

   If a static variable is unset() inside of a function, unset() destroys
   the variable and all its references.

   <?php
   function foo() {
       static $a;
       $a++;
       echo "$a\n";
       unset($a);
   }
   foo();
   foo();
   foo();
   ?>

   The above example would output:

1
2
3

   If you would like to unset() a global variable inside of a function,
   you can use the $GLOBALS array to do so:

   <?php
   function foo() {
       unset($GLOBALS['bar']);
   }
   $bar = "something";
   foo();
   ?>

     Note: Because this is a language construct and not a function, it
     cannot be called using variable functions

   See also isset(), empty(), and array_splice().
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