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php-manual-ro-20051028-1.noarch.rpm

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>Integers</TITLE
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>Manual PHP</TH
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><A
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>Înapoi</A
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>Cap. 6. Types</TD
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><DIV
CLASS="sect1"
><H1
CLASS="sect1"
><A
NAME="language.types.integer"
>Integers</A
></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 integer / GMP</A
>,
     <A
HREF="language.types.float.html"
>Floating point numbers</A
>, and
     <A
HREF="ref.bc.html"
>Arbitrary precision / BCMath</A
>
    </P
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="language.types.integer.syntax"
>Syntax</A
></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 
      <VAR
CLASS="literal"
>0</VAR
> (zero), to use hexadecimal notation precede
      the number with <VAR
CLASS="literal"
>0x</VAR
>.
      <TABLE
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
CLASS="EXAMPLE"
><TR
><TD
><DIV
CLASS="example"
><A
NAME="AEN720"
></A
><P
><B
>Exemplu 6-1. Integer literals</B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
CELLPADDING="5"
><TR
><TD
><code><font color="#000000">
<font color="#0000BB">&lt;?php<br />$a </font><font color="#007700">= </font><font color="#0000BB">1234</font><font color="#007700">; </font><font color="#FF8000">// decimal number<br /></font><font color="#0000BB">$a </font><font color="#007700">= -</font><font color="#0000BB">123</font><font color="#007700">; </font><font color="#FF8000">// a negative number<br /></font><font color="#0000BB">$a </font><font color="#007700">= </font><font color="#0000BB">0123</font><font color="#007700">; </font><font color="#FF8000">// octal number (equivalent to 83 decimal)<br /></font><font color="#0000BB">$a </font><font color="#007700">= </font><font color="#0000BB">0x1A</font><font color="#007700">; </font><font color="#FF8000">// hexadecimal number (equivalent to 26 decimal)<br /></font><font color="#0000BB">?&gt;</font>
</font>
</code></TD
></TR
></TABLE
></DIV
></TD
></TR
></TABLE
>
      Formally the possible structure for integer literals is:
      <DIV
CLASS="informalexample"
><P
></P
><A
NAME="AEN723"
></A
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
CELLPADDING="5"
><TR
><TD
><PRE
CLASS="programlisting"
>decimal     : [1-9][0-9]*
            | 0

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

octal       : 0[0-7]+

integer     : [+-]?decimal
            | [+-]?hexadecimal
            | [+-]?octal</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"
>Integer overflow</A
></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"
><P
></P
><A
NAME="AEN732"
></A
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
CELLPADDING="5"
><TR
><TD
><code><font color="#000000">
<font color="#0000BB">&lt;?php<br />$large_number </font><font color="#007700">=&nbsp;&nbsp;</font><font color="#0000BB">2147483647</font><font color="#007700">;<br /></font><font color="#0000BB">var_dump</font><font color="#007700">(</font><font color="#0000BB">$large_number</font><font color="#007700">);<br /></font><font color="#FF8000">// output: int(2147483647)<br /><br /></font><font color="#0000BB">$large_number </font><font color="#007700">=&nbsp;&nbsp;</font><font color="#0000BB">2147483648</font><font color="#007700">;<br /></font><font color="#0000BB">var_dump</font><font color="#007700">(</font><font color="#0000BB">$large_number</font><font color="#007700">);<br /></font><font color="#FF8000">// output: float(2147483648)<br /><br />// this goes also for hexadecimal specified integers:<br /></font><font color="#0000BB">var_dump</font><font color="#007700">( </font><font color="#0000BB">0x80000000 </font><font color="#007700">);<br /></font><font color="#FF8000">// output: float(2147483648)<br /><br /></font><font color="#0000BB">$million </font><font color="#007700">= </font><font color="#0000BB">1000000</font><font color="#007700">;<br /></font><font color="#0000BB">$large_number </font><font color="#007700">=&nbsp;&nbsp;</font><font color="#0000BB">50000 </font><font color="#007700">* </font><font color="#0000BB">$million</font><font color="#007700">;<br /></font><font color="#0000BB">var_dump</font><font color="#007700">(</font><font color="#0000BB">$large_number</font><font color="#007700">);<br /></font><font color="#FF8000">// output: float(50000000000)<br /></font><font color="#0000BB">?&gt;</font>
</font>
</code></TD
></TR
></TABLE
><P
></P
></DIV
>
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>Avertisment</B
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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 <VAR
CLASS="literal"
>-50000 *
        $million</VAR
>, the result will be
        <VAR
CLASS="literal"
>-429496728</VAR
>. 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.
      <VAR
CLASS="literal"
>1/2</VAR
> yields the <A
HREF="language.types.float.html"
><B
CLASS="type"
>float</B
></A
>
      <VAR
CLASS="literal"
>0.5</VAR
>. 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"
><P
></P
><A
NAME="AEN744"
></A
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
CELLPADDING="5"
><TR
><TD
><code><font color="#000000">
<font color="#0000BB">&lt;?php<br />var_dump</font><font color="#007700">(</font><font color="#0000BB">25</font><font color="#007700">/</font><font color="#0000BB">7</font><font color="#007700">);&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</font><font color="#FF8000">// float(3.5714285714286) <br /></font><font color="#0000BB">var_dump</font><font color="#007700">((int) (</font><font color="#0000BB">25</font><font color="#007700">/</font><font color="#0000BB">7</font><font color="#007700">)); </font><font color="#FF8000">// int(3)<br /></font><font color="#0000BB">var_dump</font><font color="#007700">(</font><font color="#0000BB">round</font><font color="#007700">(</font><font color="#0000BB">25</font><font color="#007700">/</font><font color="#0000BB">7</font><font color="#007700">));&nbsp;&nbsp;</font><font color="#FF8000">// float(4) <br /></font><font color="#0000BB">?&gt;</font>
</font>
</code></TD
></TR
></TABLE
><P
></P
></DIV
>
     </P
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="language.types.integer.casting"
>Converting to integer</A
></H2
><P
>&#13;       To explicitly convert a value to <A
HREF="language.types.integer.html"
><B
CLASS="type"
>integer</B
></A
>, use either
       the <VAR
CLASS="literal"
>(int)</VAR
> or the <VAR
CLASS="literal"
>(integer)</VAR
> 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"
>From <A
HREF="language.types.boolean.html"
>booleans</A
></A
></H3
><P
>&#13;        <TT
CLASS="constant"
><B
>FALSE</B
></TT
> will yield 
        <VAR
CLASS="literal"
>0</VAR
> (zero), and <TT
CLASS="constant"
><B
>TRUE</B
></TT
> 
        will yield <VAR
CLASS="literal"
>1</VAR
> (one).
       </P
></DIV
><DIV
CLASS="sect3"
><H3
CLASS="sect3"
><A
NAME="language.types.integer.casting.from-float"
>From <A
HREF="language.types.float.html"
>floating point numbers</A
></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 <VAR
CLASS="literal"
>+/- 2.15e+9 = 2^31</VAR
>), 
        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
CLASS="warning"
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><TR
><TD
ALIGN="CENTER"
><B
>Avertisment</B
></TD
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><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"
><P
></P
><A
NAME="AEN774"
></A
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
CELLPADDING="5"
><TR
><TD
><code><font color="#000000">
<font color="#0000BB">&lt;?php<br /></font><font color="#007700">echo (int) ( (</font><font color="#0000BB">0.1</font><font color="#007700">+</font><font color="#0000BB">0.7</font><font color="#007700">) * </font><font color="#0000BB">10 </font><font color="#007700">); </font><font color="#FF8000">// echoes 7!<br /></font><font color="#0000BB">?&gt;</font>
</font>
</code></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"
>From strings</A
></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"
>From other types</A
></H3
><P
>&#13;        <DIV
CLASS="caution"
><P
></P
><TABLE
CLASS="caution"
BORDER="1"
WIDTH="100%"
><TR
><TD
ALIGN="CENTER"
><B
>Aten&#254;ie</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
></TABLE
></DIV
>
       </P
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