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

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>Integers</TITLE
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><DIV
CLASS="sect1"
><H1
CLASS="sect1"
><A
NAME="language.types.integer"
></A
>Integers</H1
><P
>&#13;     An <A
HREF="language.types.integer.html"
><B
CLASS="type"
>integer</B
></A
> is a number of the set 
     Z = {..., -2, -1, 0, 1, 2, ...}.
    </P
><P
>&#13;     See also:
     <A
HREF="ref.gmp.html"
>Arbitrary length integers</A
> and
     <A
HREF="language.types.float.html"
>Floating point numbers</A
>
    </P
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="language.types.integer.syntax"
></A
>Syntax</H2
><P
>&#13;      Integers can be specified in decimal (10-based), hexadecimal (16-based)
      or octal (8-based) notation, optionally preceded by a sign (- or +).
     </P
><P
>&#13;      If you use the octal notation, you must precede the number with a 
      <TT
CLASS="literal"
>0</TT
> (zero), to use hexadecimal notation precede
      the number with <TT
CLASS="literal"
>0x</TT
>.
      <TABLE
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CLASS="EXAMPLE"
><TR
><TD
><DIV
CLASS="example"
><A
NAME="AEN3302"
></A
><P
><B
>Example 7-1. Integer literals</B
></P
><TABLE
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><TR
><TD
><PRE
CLASS="php"
>&#60;?php
$a = 1234; # decimal number
$a = -123; # a negative number
$a = 0123; # octal number (equivalent to 83 decimal)
$a = 0x1A; # hexadecimal number (equivalent to 26 decimal)
?&#62;</PRE
></TD
></TR
></TABLE
></DIV
></TD
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></TABLE
>
      Formally the possible structure for integer literals is:
      <DIV
CLASS="informalexample"
><A
NAME="AEN3305"
></A
><P
></P
><TABLE
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><TD
><PRE
CLASS="programlisting"
>&#60;?php
decimal     : [1-9][0-9]*
            | 0

hexadecimal : 0[xX][0-9a-fA-F]+

octal       : 0[0-7]+

integer     : [+-]?decimal
            | [+-]?hexadecimal
            | [+-]?octal
?&#62;</PRE
></TD
></TR
></TABLE
><P
></P
></DIV
>
      The size of an integer is platform-dependent, although a 
      maximum value of about two billion is the usual value 
      (that's 32 bits signed). PHP does not support unsigned
      integers.
     </P
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="language.types.integer.overflow"
></A
>Integer overflow</H2
><P
>&#13;      If you specify a number beyond the bounds of the <A
HREF="language.types.integer.html"
><B
CLASS="type"
>integer</B
></A
>
      type, it will be interpreted as a <A
HREF="language.types.float.html"
><B
CLASS="type"
>float</B
></A
> instead. Also, if
      you perform an operation that results in a number beyond the bounds of
      the <A
HREF="language.types.integer.html"
><B
CLASS="type"
>integer</B
></A
> type, a <A
HREF="language.types.float.html"
><B
CLASS="type"
>float</B
></A
> will be returned
      instead.

      <DIV
CLASS="informalexample"
><A
NAME="AEN3314"
></A
><P
></P
><TABLE
BORDER="0"
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><TR
><TD
><PRE
CLASS="php"
>&#60;?php
$large_number =  2147483647;
var_dump($large_number);
// output: int(2147483647)

$large_number =  2147483648;
var_dump($large_number);
// output: float(2147483648)

// this goes also for hexadecimal specified integers:
var_dump( 0x80000000 );
// output: float(2147483648)

$million = 1000000;
$large_number =  50000 * $million;
var_dump($large_number);
// output: float(50000000000)
?&#62;</PRE
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>
      <DIV
CLASS="warning"
><P
></P
><TABLE
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><TD
ALIGN="CENTER"
><B
>Warning</B
></TD
></TR
><TR
><TD
ALIGN="LEFT"
><P
>&#13;        Unfortunately, there was a bug in PHP so that this
        does not always work correctly when there are negative numbers
        involved. For example: when you do <TT
CLASS="literal"
>-50000 *
        $million</TT
>, the result will be
        <TT
CLASS="literal"
>-429496728</TT
>. However, when both operands are
        positive there is no problem.
       </P
><P
>&#13;        This is solved in PHP 4.1.0.
       </P
></TD
></TR
></TABLE
></DIV
>
     </P
><P
>&#13;      There is no integer division operator in PHP.
      <TT
CLASS="literal"
>1/2</TT
> yields the <A
HREF="language.types.float.html"
><B
CLASS="type"
>float</B
></A
>
      <TT
CLASS="literal"
>0.5</TT
>. You can cast the value to
      an integer to always round it downwards, or you can
      use the <A
HREF="function.round.html"
><B
CLASS="function"
>round()</B
></A
> function.
      <DIV
CLASS="informalexample"
><A
NAME="AEN3326"
></A
><P
></P
><TABLE
BORDER="0"
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><TR
><TD
><PRE
CLASS="php"
>&#60;?php
var_dump(25/7);         // float(3.5714285714286) 
var_dump((int) (25/7)); // int(3)
var_dump(round(25/7));  // float(4) 
?&#62;</PRE
></TD
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><P
></P
></DIV
>
     </P
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="language.types.integer.casting"
></A
>Converting to integer</H2
><P
>&#13;       To explicitly convert a value to <A
HREF="language.types.integer.html"
><B
CLASS="type"
>integer</B
></A
>, use either
       the <TT
CLASS="literal"
>(int)</TT
> or the <TT
CLASS="literal"
>(integer)</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 an <A
HREF="language.types.integer.html"
><B
CLASS="type"
>integer</B
></A
> argument.
       You can also convert a value to integer with the function
       <A
HREF="function.intval.html"
><B
CLASS="function"
>intval()</B
></A
>.
      </P
><P
>&#13;       See also <A
HREF="language.types.type-juggling.html"
>type-juggling</A
>.
      </P
><DIV
CLASS="sect3"
><H3
CLASS="sect3"
><A
NAME="language.types.integer.casting.from-boolean"
></A
>From <A
HREF="language.types.boolean.html"
>booleans</A
></H3
><P
>&#13;        <TT
CLASS="constant"
><B
>FALSE</B
></TT
> will yield 
        <TT
CLASS="literal"
>0</TT
> (zero), and <TT
CLASS="constant"
><B
>TRUE</B
></TT
> 
        will yield <TT
CLASS="literal"
>1</TT
> (one).
       </P
></DIV
><DIV
CLASS="sect3"
><H3
CLASS="sect3"
><A
NAME="language.types.integer.casting.from-float"
></A
>From <A
HREF="language.types.float.html"
>floating point numbers</A
></H3
><P
>&#13;        When converting from float to integer, the number will
        be rounded <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>towards zero</I
></SPAN
>.
       </P
><P
>&#13;        If the float is beyond the boundaries of integer
        (usually <TT
CLASS="literal"
>+/- 2.15e+9 = 2^31</TT
>), 
        the result is undefined, since the float hasn't
        got enough precision to give an exact integer result.
        No warning, not even a notice will be issued in this 
        case!
       </P
><DIV
CLASS="warning"
><P
></P
><TABLE
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><TR
><TD
ALIGN="CENTER"
><B
>Warning</B
></TD
></TR
><TR
><TD
ALIGN="LEFT"
><P
>&#13;        Never cast an unknown fraction to <A
HREF="language.types.integer.html"
><B
CLASS="type"
>integer</B
></A
>, as this can
        sometimes lead to unexpected results.
        <DIV
CLASS="informalexample"
><A
NAME="AEN3356"
></A
><P
></P
><TABLE
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><TR
><TD
><PRE
CLASS="php"
>&#60;?php
echo (int) ( (0.1+0.7) * 10 ); // echoes 7!
?&#62;</PRE
></TD
></TR
></TABLE
><P
></P
></DIV
>
        
        See for more information the <A
HREF="language.types.float.html#warn.float-precision"
>warning 
        about float-precision</A
>.
       </P
></TD
></TR
></TABLE
></DIV
></DIV
><DIV
CLASS="sect3"
><H3
CLASS="sect3"
><A
NAME="language.types.integer.casting.from-string"
></A
>From strings</H3
><P
>&#13;        See <A
HREF="language.types.string.html#language.types.string.conversion"
>String 
        conversion to numbers</A
>
       </P
></DIV
><DIV
CLASS="sect3"
><H3
CLASS="sect3"
><A
NAME="language.types.integer.casting.from-other"
></A
>From other types</H3
><P
>&#13;        <DIV
CLASS="caution"
><P
></P
><TABLE
CLASS="caution"
BORDER="1"
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><TR
><TD
ALIGN="CENTER"
><B
>Caution</B
></TD
></TR
><TR
><TD
ALIGN="LEFT"
><P
>&#13;          Behaviour of converting to integer is undefined for other
          types. Currently, the behaviour is the same as if the value
          was first <A
HREF="language.types.boolean.html#language.types.boolean.casting"
>converted to boolean</A
>. However, do
          <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>not</I
></SPAN
> rely on this behaviour, as it can
          change without notice.
         </P
></TD
></TR
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>
       </P
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