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php-manual-en-4.3.0-2mdk.noarch.rpm

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><H1
><A
NAME="function.unset"
></A
>unset</H1
><DIV
CLASS="refnamediv"
><A
NAME="AEN94516"
></A
><P
>    (PHP 3, PHP 4 )</P
>unset&nbsp;--&nbsp;Unset a given variable</DIV
><DIV
CLASS="refsect1"
><A
NAME="AEN94519"
></A
><H2
>Description</H2
>void <B
CLASS="methodname"
>unset</B
> ( mixed var [, mixed var [, ...]])<BR
></BR
><DIV
CLASS="note"
><BLOCKQUOTE
CLASS="note"
><P
><B
>Note: </B
>
      <B
CLASS="function"
>unset()</B
> is a language construct.
     </P
></BLOCKQUOTE
></DIV
><P
>&#13;     <B
CLASS="function"
>unset()</B
> destroys the specified variables. Note
     that in PHP 3, <B
CLASS="function"
>unset()</B
> will always return <TT
CLASS="constant"
><B
>TRUE</B
></TT
>
     (actually, the integer value 1). In PHP 4, however,
     <B
CLASS="function"
>unset()</B
> is no longer a true function: it is
     now a statement. As such no value is returned, and attempting to
     take the value of <B
CLASS="function"
>unset()</B
> results in a parse
     error.
    </P
><P
>&#13;     <TABLE
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
CLASS="EXAMPLE"
><TR
><TD
><DIV
CLASS="example"
><A
NAME="AEN94542"
></A
><P
><B
>Example 1. <B
CLASS="function"
>unset()</B
> example</B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
CELLPADDING="5"
><TR
><TD
><PRE
CLASS="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);</PRE
></TD
></TR
></TABLE
></DIV
></TD
></TR
></TABLE
>
    </P
><P
>&#13;     The behavior of <B
CLASS="function"
>unset()</B
> inside of a function
     can vary depending on what type of variable you are attempting to
     destroy.
    </P
><P
>&#13;     If a globalized variable is <B
CLASS="function"
>unset()</B
> inside of
     a function, only the local variable is destroyed.  The variable
     in the calling environment will retain the same value as before
     <B
CLASS="function"
>unset()</B
> was called.
     <DIV
CLASS="informalexample"
><A
NAME="AEN94551"
></A
><P
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
CELLPADDING="5"
><TR
><TD
><PRE
CLASS="php"
>function destroy_foo() {
    global $foo;
    unset($foo);
}

$foo = 'bar';
destroy_foo();
echo $foo;</PRE
></TD
></TR
></TABLE
><P
></P
></DIV
>
     The above example would output:
     <DIV
CLASS="informalexample"
><A
NAME="AEN94553"
></A
><P
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
CELLPADDING="5"
><TR
><TD
><PRE
CLASS="screen"
>bar</PRE
></TD
></TR
></TABLE
><P
></P
></DIV
>
    </P
><P
>&#13;     If a variable that is PASSED BY REFERENCE is
     <B
CLASS="function"
>unset()</B
> inside of a function, only the local
     variable is destroyed.  The variable in the calling environment
     will retain the same value as before <B
CLASS="function"
>unset()</B
>
     was called.
     <DIV
CLASS="informalexample"
><A
NAME="AEN94558"
></A
><P
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
CELLPADDING="5"
><TR
><TD
><PRE
CLASS="php"
>function foo(&#38;$bar) {
    unset($bar);
    $bar = "blah";
}

$bar = 'something';
echo "$bar\n";

foo($bar);
echo "$bar\n";</PRE
></TD
></TR
></TABLE
><P
></P
></DIV
>
     The above example would output:
     <DIV
CLASS="informalexample"
><A
NAME="AEN94560"
></A
><P
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
CELLPADDING="5"
><TR
><TD
><PRE
CLASS="screen"
>something
something</PRE
></TD
></TR
></TABLE
><P
></P
></DIV
>
    </P
><P
>&#13;     If a static variable is <B
CLASS="function"
>unset()</B
> inside of a
     function, <B
CLASS="function"
>unset()</B
> destroyes the variable and all 
     its references.
     <DIV
CLASS="informalexample"
><A
NAME="AEN94565"
></A
><P
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
CELLPADDING="5"
><TR
><TD
><PRE
CLASS="php"
>function foo() {
    static $a;
    $a++;
    echo "$a\n";
    unset($a);
}

foo();
foo();
foo();</PRE
></TD
></TR
></TABLE
><P
></P
></DIV
>
     The above example would output:
     <DIV
CLASS="informalexample"
><A
NAME="AEN94567"
></A
><P
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
CELLPADDING="5"
><TR
><TD
><PRE
CLASS="screen"
>1
2
3</PRE
></TD
></TR
></TABLE
><P
></P
></DIV
>
    </P
><P
>&#13;     If you would like to <B
CLASS="function"
>unset()</B
> a global variable
     inside of a function, you can use
     the <TT
CLASS="varname"
>$GLOBALS</TT
> array to do so:
     <DIV
CLASS="informalexample"
><A
NAME="AEN94572"
></A
><P
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
CELLPADDING="5"
><TR
><TD
><PRE
CLASS="php"
>function foo() {
    unset($GLOBALS['bar']);
}

$bar = "something";
foo();</PRE
></TD
></TR
></TABLE
><P
></P
></DIV
>
    </P
><P
>&#13;     See also <A
HREF="function.isset.html"
><B
CLASS="function"
>isset()</B
></A
> and
     <A
HREF="function.empty.html"
><B
CLASS="function"
>empty()</B
></A
>.
    </P
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