File: function.unset.html

package info (click to toggle)
php3 3%3A3.0.18-0potato1.1
links: PTS
area: main
in suites: potato
size: 17,736 kB
ctags: 11,198
sloc: ansic: 108,120; sh: 2,512; php: 2,024; yacc: 1,887; makefile: 1,038; perl: 537; pascal: 238; awk: 90; cpp: 28; sql: 11
file content (499 lines) | stat: -rw-r--r-- 6,191 bytes
parent folder | download | duplicates (3)
<HTML
><HEAD
><TITLE
>unset</TITLE
><META
NAME="GENERATOR"
CONTENT="Modular DocBook HTML Stylesheet Version 1.57"><LINK
REL="HOME"
TITLE="PHP Manual"
HREF="manual.html"><LINK
REL="UP"
TITLE="Variable Functions"
HREF="ref.var.html"><LINK
REL="PREVIOUS"
TITLE="unserialize"
HREF="function.unserialize.html"><LINK
REL="NEXT"
TITLE="var_dump"
HREF="function.var-dump.html"><META
NAME="HTTP_EQUIV"
CONTENT="text/html; charset=ISO-8859-1"></HEAD
><BODY
CLASS="refentry"
BGCOLOR="#FFFFFF"
TEXT="#000000"
LINK="#0000FF"
VLINK="#840084"
ALINK="#0000FF"
><DIV
CLASS="NAVHEADER"
><TABLE
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TH
COLSPAN="3"
ALIGN="center"
>PHP Manual</TH
></TR
><TR
><TD
WIDTH="10%"
ALIGN="left"
VALIGN="bottom"
><A
HREF="function.unserialize.html"
>Prev</A
></TD
><TD
WIDTH="80%"
ALIGN="center"
VALIGN="bottom"
></TD
><TD
WIDTH="10%"
ALIGN="right"
VALIGN="bottom"
><A
HREF="function.var-dump.html"
>Next</A
></TD
></TR
></TABLE
><HR
ALIGN="LEFT"
WIDTH="100%"></DIV
><H1
><A
NAME="function.unset"
>unset</A
></H1
><DIV
CLASS="refnamediv"
><A
NAME="AEN39102"
></A
><P
>    (unknown)</P
>unset&nbsp;--&nbsp;Unset a given variable</DIV
><DIV
CLASS="refsect1"
><A
NAME="AEN39105"
></A
><H2
>Description</H2
><DIV
CLASS="funcsynopsis"
><A
NAME="AEN39107"
></A
><P
></P
><P
><CODE
><CODE
CLASS="FUNCDEF"
>int <B
CLASS="function"
>unset</B
></CODE
> (mixed var [, mixed var [, ...]])</CODE
></P
><P
></P
></DIV
><P
>&#13;     <B
CLASS="function"
>unset()</B
> destroys the specified variables and
     returns true.
    </P
><P
>&#13;     <TABLE
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
CLASS="EXAMPLE"
><TR
><TD
><DIV
CLASS="example"
><A
NAME="AEN39122"
></A
><P
><B
>Example 1. <B
CLASS="function"
>Unset()</B
> example</B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="programlisting"
>&#13;// 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="AEN39131"
></A
><P
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="programlisting"
>&#13;function destroy_foo() {
    global $foo;
    unset($foo);
}

$foo = 'bar';
destroy_foo();
echo $foo;
      </PRE
></TD
></TR
></TABLE
><P
></P
></DIV
>
     The above example would output:
     <DIV
CLASS="informalexample"
><A
NAME="AEN39133"
></A
><P
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="programlisting"
>&#13;bar
      </PRE
></TD
></TR
></TABLE
><P
></P
></DIV
>
    </P
><P
>&#13;     If a variable that is PASSED BY REFERENCE is
     <B
CLASS="function"
>unset()</B
> inside of a function, only the local
     variable is destroyed.  The variable in the calling environment
     will retain the same value as before <B
CLASS="function"
>unset()</B
>
     was called.
     <DIV
CLASS="informalexample"
><A
NAME="AEN39138"
></A
><P
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="programlisting"
>&#13;function foo(&#38;$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="AEN39140"
></A
><P
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="programlisting"
>&#13;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
> unsets the reference to the
     static variable, rather than the static variable itself.
     <DIV
CLASS="informalexample"
><A
NAME="AEN39145"
></A
><P
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="programlisting"
>&#13;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="AEN39147"
></A
><P
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="programlisting"
>&#13;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="parameter"
><I
>$GLOBALS</I
></TT
> array to do so:
     <DIV
CLASS="informalexample"
><A
NAME="AEN39152"
></A
><P
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="programlisting"
>&#13;function foo() {
    unset($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
></DIV
><DIV
CLASS="NAVFOOTER"
><HR
ALIGN="LEFT"
WIDTH="100%"><TABLE
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
><A
HREF="function.unserialize.html"
>Prev</A
></TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="manual.html"
>Home</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
><A
HREF="function.var-dump.html"
>Next</A
></TD
></TR
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
>unserialize</TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="ref.var.html"
>Up</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
>var_dump</TD
></TR
></TABLE
></DIV
></BODY
></HTML
>