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

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CLASS="sect1"
><H1
CLASS="sect1"
><A
NAME="control-structures.declare"
></A
><TT
CLASS="literal"
>declare</TT
></H1
><P
>&#13;    The <TT
CLASS="literal"
>declare</TT
> construct is used to
    set execution directives for a block of code.
    The syntax of <TT
CLASS="literal"
>declare</TT
> is similar to
    the syntax of other flow control constructs:
    <DIV
CLASS="informalexample"
><A
NAME="AEN5063"
></A
><P
></P
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><PRE
CLASS="programlisting"
>declare (directive) statement</PRE
></TD
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><P
></P
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>
   </P
><P
>&#13;    The <TT
CLASS="literal"
>directive</TT
> section allows the
    behavior of the <TT
CLASS="literal"
>declare</TT
> block to
    be set.
    Currently only one directive is recognized: the
    <TT
CLASS="literal"
>ticks</TT
> directive. (See below for more
    information on the
    <A
HREF="control-structures.declare.html#control-structures.declare.ticks"
>ticks</A
>
    directive)
   </P
><P
>&#13;    The <TT
CLASS="literal"
>statement</TT
> part of the
    <TT
CLASS="literal"
>declare</TT
> block will be executed -- how
    it is executed and what side effects occur during execution
    may depend on the directive set in the
    <TT
CLASS="literal"
>directive</TT
> block.
   </P
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="control-structures.declare.ticks"
></A
>Ticks</H2
><P
>A tick is an event that occurs for every
    <TT
CLASS="replaceable"
><I
>N</I
></TT
> low-level statements executed
    by the parser within the <TT
CLASS="literal"
>declare</TT
> block.
    The value for <TT
CLASS="replaceable"
><I
>N</I
></TT
> is specified
    using <TT
CLASS="literal"
>ticks=<TT
CLASS="replaceable"
><I
>N</I
></TT
></TT
>
    within the <TT
CLASS="literal"
>declare</TT
> blocks's
    <TT
CLASS="literal"
>directive</TT
> section.
   </P
><P
>&#13;    The event(s) that occur on each tick are specified using the
    <A
HREF="function.register-tick-function.html"
><B
CLASS="function"
>register_tick_function()</B
></A
>. See the example 
    below for more details. Note that more than one event can occur
    for each tick.
   </P
><P
>&#13;    <TABLE
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><TR
><TD
><DIV
CLASS="example"
><A
NAME="AEN5087"
></A
><P
><B
>Example 12-1. Profile a section of PHP code</B
></P
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><PRE
CLASS="php"
>&#60;?php
// A function that records the time when it is called
function profile ($dump = FALSE)
{
    static $profile;

    // Return the times stored in profile, then erase it
    if ($dump) {
        $temp = $profile;
        unset ($profile);
        return ($temp);
    }

    $profile[] = microtime ();
}

// Set up a tick handler
register_tick_function("profile");

// Initialize the function before the declare block
profile ();

// Run a block of code, throw a tick every 2nd statement
declare (ticks=2) {
    for ($x = 1; $x &#60; 50; ++$x) {
        echo similar_text (md5($x), md5($x*$x)), "&#60;br /&#62;;";
    }
}

// Display the data stored in the profiler
print_r (profile (TRUE));
?&#62;</PRE
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>
    The example profiles the PHP code within the 'declare'
    block, recording the time at which every second low-level
    statement in the block was executed. This information can
    then be used to find the slow areas within particular
    segments of code. This process can be performed using other
    methods: using ticks is more convenient and easier to
    implement.
   </P
><P
>&#13;    Ticks are well suited for debugging, implementing simple
    multitasking, backgrounded I/O and many other tasks.
   </P
><P
>&#13;    See also <A
HREF="function.register-tick-function.html"
><B
CLASS="function"
>register_tick_function()</B
></A
> and
    <A
HREF="function.unregister-tick-function.html"
><B
CLASS="function"
>unregister_tick_function()</B
></A
>.
   </P
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