Sophie: php-manual-en-4.3.0-2mdk noarch

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

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><DIV
CLASS="sect1"
><H1
CLASS="sect1"
><A
NAME="language.types.boolean"
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>Booleans</H1
><P
>&#13;     This is the easiest type. A <A
HREF="language.types.boolean.html"
><B
CLASS="type"
>boolean</B
></A
> expresses a 
     truth value. It can be either <TT
CLASS="constant"
><B
>TRUE</B
></TT
> or <TT
CLASS="constant"
><B
>FALSE</B
></TT
>. 
    </P
><DIV
CLASS="note"
><BLOCKQUOTE
CLASS="note"
><P
><B
>Note: </B
>
      The boolean type was introduced in PHP 4.
     </P
></BLOCKQUOTE
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="language.types.boolean.syntax"
></A
>Syntax</H2
><P
>&#13;      To specify a boolean literal, use either the keyword <TT
CLASS="constant"
><B
>TRUE</B
></TT
> 
      or <TT
CLASS="constant"
><B
>FALSE</B
></TT
>. Both are case-insensitive.
      <DIV
CLASS="informalexample"
><A
NAME="AEN3237"
></A
><P
></P
><TABLE
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><TR
><TD
><PRE
CLASS="php"
>&#60;?php
$foo = True; // assign the value TRUE to $foo
?&#62;</PRE
></TD
></TR
></TABLE
><P
></P
></DIV
>
     </P
><P
>&#13;      Usually you 
      use some kind of <A
HREF="language.operators.html"
>operator</A
>
      which returns a <A
HREF="language.types.boolean.html"
><B
CLASS="type"
>boolean</B
></A
> value, and then pass it 
      on to a <A
HREF="control-structures.html"
>control
      structure</A
>.
      <DIV
CLASS="informalexample"
><A
NAME="AEN3243"
></A
><P
></P
><TABLE
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><TD
><PRE
CLASS="php"
>&#60;?php
// == is an operator which test
// equality and returns a boolean
if ($action == "show_version") {
    echo "The version is 1.23";
}

// this is not necessary...
if ($show_separators == TRUE) {
    echo "&#60;hr&#62;\n";
}

// ...because you can simply type
if ($show_separators) {
    echo "&#60;hr&#62;\n";
}
?&#62;</PRE
></TD
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><P
></P
></DIV
>
     </P
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="language.types.boolean.casting"
></A
>Converting to boolean</H2
><P
>&#13;       To explicitly convert a value to <A
HREF="language.types.boolean.html"
><B
CLASS="type"
>boolean</B
></A
>, use either
       the <TT
CLASS="literal"
>(bool)</TT
> or the <TT
CLASS="literal"
>(boolean)</TT
> cast.
       However, in most cases you do not need to use the cast, since a value
       will be automatically converted if an operator, function or 
       control structure requires a <A
HREF="language.types.boolean.html"
><B
CLASS="type"
>boolean</B
></A
> argument.
      </P
><P
>&#13;       See also <A
HREF="language.types.type-juggling.html"
>Type Juggling</A
>.
      </P
><P
>&#13;       When converting to <A
HREF="language.types.boolean.html"
><B
CLASS="type"
>boolean</B
></A
>, the following values 
       are considered <TT
CLASS="constant"
><B
>FALSE</B
></TT
>:
  
       <P
></P
><UL
><LI
><P
>the <A
HREF="language.types.boolean.html"
>boolean</A
> 
          <TT
CLASS="constant"
><B
>FALSE</B
></TT
> itself</P
></LI
><LI
><P
>the <A
HREF="language.types.integer.html"
>integer</A
> 0 (zero) </P
></LI
><LI
><P
>the <A
HREF="language.types.float.html"
>float</A
> 
         0.0 (zero) </P
></LI
><LI
><P
>the empty <A
HREF="language.types.string.html"
>string</A
>, and the <A
HREF="language.types.string.html"
>string</A
>
           "0"</P
></LI
><LI
><P
>an <A
HREF="language.types.array.html"
>array</A
> 
         with zero elements</P
></LI
><LI
><P
>an <A
HREF="language.types.object.html"
>object</A
> 
         with zero member variables</P
></LI
><LI
><P
>the special type <A
HREF="language.types.null.html"
>NULL</A
> (including unset variables)
         </P
></LI
></UL
>
       
       Every other value is considered <TT
CLASS="constant"
><B
>TRUE</B
></TT
> (including any 
       <A
HREF="language.types.resource.html"
>resource</A
>).
       <DIV
CLASS="warning"
><P
></P
><TABLE
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><TD
ALIGN="CENTER"
><B
>Warning</B
></TD
></TR
><TR
><TD
ALIGN="LEFT"
><P
>&#13;         <TT
CLASS="literal"
>-1</TT
> is considered  
         <TT
CLASS="constant"
><B
>TRUE</B
></TT
>, like any other non-zero (whether negative
         or positive) number!
        </P
></TD
></TR
></TABLE
></DIV
>
       <DIV
CLASS="informalexample"
><A
NAME="AEN3287"
></A
><P
></P
><TABLE
BORDER="0"
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CELLPADDING="5"
><TR
><TD
><PRE
CLASS="php"
>&#60;?php
echo gettype((bool) "");        // bool(false)
echo gettype((bool) 1);         // bool(true)
echo gettype((bool) -2);        // bool(true)
echo gettype((bool) "foo");     // bool(true)
echo gettype((bool) 2.3e5);     // bool(true)
echo gettype((bool) array(12)); // bool(true)
echo gettype((bool) array());   // bool(false)
?&#62;</PRE
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