How in the world do you know that "code will run faster" ?
Implementing your suggestion would take quite a lot of changes to the
internals of PHP. Instead of just a global and a current symbol table, we
would now need basically an unlimited number of symbol tables and every
variable lookup would become more complex. Ergo it would slow things
down.
-Rasmus
On Mon, 21 Oct 2002, NTPT wrote:
> Hi.
> I have some idea and suggestion how to extend PHP language a bit in some
> way. That may probably lead to increasing of php flexibility, allow more
> modular coding to be done etc....
>
>
> My sugestion is simple:
> Allow PHP programmer to explicitelly told , WHAT variable scope will be
> used inside user defined functions.
>
> In the traditional approach (afaik , i use php 4.2.2 ), as is described in
> the manual of php there a diferent varable scopes for each functions , only
> syntax " global $valuename" ; can lead to use variables global. This aproach
> is traditional and well known and is sufficient for most tasks.(I say
> sufficient, not effective...). My idea is going a bit behind it.
>
> I suggest to introduce new keyword(s) or function(s) into the PHP language
> definiton
> (i suggest syntax like "var_scope scope" or var_scope("scope") )
>
> That keywords SHOULD be used in user defined functions to EXPLICITLY
> define, WHAT kind of variable scope will be used inside this function.
>
> scope can be either
>
> 'local' = it means, that all variables used in this function have a local
> scope only.(it means like traditional behavior of php and its variable
> scopes until now )
>
> 'global' = each variable used in the function is from global scope. Similar
> to "global $variable_1,$variable_2........... $each variable used in the
> main execution line of the script"
>
> 'caller' or 'inherit' This is MOST USEFUL part of the idea . Function
> variable scope is the SAME as from where the function was called. (if
> functino bar(),with have var_scope set to 'caller', is called from function
> foo() it have the same variable scope as function foo(), almost like the
> code of function bar() was included (by include "something" ) somewhere
> inside foo() )
>
>
> A little example code for demonstrating idea of the syntax and how it should
> work:
> */
> <?
>
> $a=10;
>
> echo "Varaible $a".$a;
> .
> $foo_output =foo();
> echo "<br>value returnded by foo() ".$foooutput;
> echo "<br>value $a after calling foo() but before calling bar() ".$a;
>
> $bar_output=bar();
> echo "<br>value returnded by bar() ".$bar_output;
> .
> .
> echo "<br>value $a after calling bar() ".$a;
>
> function foo()
> {
> $a=20;
> echo "$a inside function foo() = ".$a
> /* $bar_inside foo = bar();
> echo "Variable $a inside function foo() after calling bar()".$a;
>
> */
> .
> .
>
> return $a;
>
> }
>
>
> function bar()
> {
> var_scope caller // we have the SAME variable scope as from where we are
> called
> $a=100;
> .
> .
> .
> return $a;
> }
> ?>
> this should return : (with comments behind // )
>
> Varaible $a" 10
> $a inside function foo() = 20
> value returnded by foo() 20
> value $a after calling foo() but before calling bar() 10
> value returnded by bar() 100
> value $a after calling bar() 100 // var_scope is set to 'caller', so $a
> in global scope is modified inside bar() the some way, as if global $a was
> used )
>
> if you uncomment lines in bar()....
>
> Varaible $a" 10
> $a inside function foo() = 20
> Variable $a inside function foo() after calling bar() 100 // var_scope in
> function bar() is set to caller, so $a IN SCOPE of foo() ONLY is modified
> inside bar().
>
> value returnded by foo() 100
> value $a after calling foo() but before calling bar() 10 // var_scope in
> function bar() is set to caller, so $a IN GLOBAL SCOPE is NOT modified
> inside bar().
> value returnded by bar() 100
> value $a after calling bar() 100 // var_scope is set to caller, so $a in
> global scope is modified inside bar() the some waz, as if global $a was used
>
>
> For WHAT it could be useful ??
>
>
> for example for writing a databaze extraction layer of any aplication.
> common real life situations are similar like in this example code
> (simplified and abstracted from real life code of PHP application I
> currently write )....
>
> <?
> .
> .
> .
> .
> do something
> .
> .
> .
> // now you need a call subroutine
>
> $something=foo('cats','dogs','horses');
> .
> $different=bar('mices','meat','gras');
> .
> .
> .
> .
>
> function foo($data_1,$data_2,$data_3)
> {
> global $spojeni;
> .
> .
> do something here with $data_1,$data_2,$data_3.........
> .
> .
> .
>
>
> $sqlstring="select * from example_table where mouse_catching='$data1' AND
> sniffing='$data_2' AND riding='$data_3'"
> $result=pg_exec($spojeni,$sqlstring);
>
> // code, that validate if db done that we want, if select return exactly
> one line or if there is a some data inconsistrency etc etc. The following
> code (wery simplified snipplet from real life situation) is almost the same
> inside many of the functions
> if ($result)
> {
> $lines=pg_numrows($result);
> if ($lines <1)
> {
> do something if we have no records. Typicaly display error message
> ,repeat quyery with default values etc.....
> }
> if ($lines >1)
> {
> oops, database is inconsistent. exactly one line should be returned. Stop
> script
> die("database EXAMPLE TABLE have data inconsistency. contact server
> admin now")
> }
>
> if ($lines=1)
> {
> $retval= pg_fetch_array($result,0); // we have what we are looking for...
> }
>
> }
> else
> {
> die("No select from example_table")
> }
> //end of the validating code
> return $retval;
> }
>
>
> function bar($data_1,$data_2,$data_3)
> {
> global $spojeni;
> $sqlstring="select * from other_example_table where bla bla bla ...... some
> thuing'";
> // bla bla bla and similar as in foo()
>
>
> }
> ?>
>
>
> in traditional approach, it could be done better and flexibile only by few
> and limited ways.
> One of then is to use for example include "" like this:
>
> <?
> function foo($data_1,$data_2,$data_3)
> {
> global $spojeni;
> .
> .
> do something here with $data_1,$data_2,$data_3.........
> .
> .
> .
>
>
> $sqlstring="select * from example_table where mouse_catching='$data1' AND
> sniffing='$data_2' AND riding='$data_3'"
> $result=pg_exec($spojeni,$sqlstring);
>
> // code, that validate if db done that we want, if select return exactlz
> one line or if there is a some data inconsistrency etc etc. The following
> code (wery simplified snipplet from real life situation) is almost the same
> inside many of the functions
>
> include "database_code.php" ; // all validating code is moved inside
> database_code.php3 , so it could be uset more frequently in more functions ;
>
> //end of the validating code
>
> return $retval;
> }
> ?>
>
> but it have several caveats. For example , database_code.php can be a big
> fat file with lot of lines and tests and if function foo() is called
> somewhere from loop, it will be included each itteration and it menas,
> that in each iterration will be parsed for errors (fix me if i am wrong...)
> etc etc and loop can have hunderds or thousends itteration and i iffraid, it
> could have a serious performance impact.
>
>
> The code rewriten for using my suggested "explicitly setiing of variable
> scope inside function" language extension, exactly "var_scope caller;" will
> look like this ( the following example uses "get_var_scope()" function, that
> is part of the sugested extensions to examine WHAT variable scope we are
> currently have and "local_vars $varname" (with list variables, that are
> intendet to be LOCAL ONLY , it act like oposite of "globals") ) :
>
> <?
>
> $database="postgres";
> .
> .
> .
> .
> do something
> .
> .
> .
> // now zou need a call subroutine
>
> $something=foo('cats','dogs','horses');
> .
> $different=bar('mices','meat','gras');
> .
> .
> .
> .
>
> function foo($data_1,$data_2,$data_3)
> {
> global $spojeni,$database;
> .
> .
> do something here with $data_1,$data_2,$data_3.........
> .
> .
> .
>
>
> $sqlstring="select * from example_table where mouse_catching='$data1' AND
> sniffing='$data_2' AND riding='$data_3'"
> $retval= db_execute_query($sqlsting);
> return $retval;
> }
>
>
> function bar($data_1,$data_2,$data_3)
> {
> global $spojeni;
> $sqlstring="select * from other_example_table where mouse_catching='$data1'
> AND sniffing='$data_2' AND riding='$data_3'";
> $retval= db_execute_query($sqlsting);
> return $retval;
> }
>
>
>
> function db_execute_query($sqlstring)
> {
> // executing database query, making all tests that everything went good
> etc... simple database abstraction layer included as bonus :o) ......
>
> var_scope caller; // ve inherit variable scope from where we are called
> global $database; // we need name of the database engine
> local_vars $i,$j,$k,$partial_result,$retval,$sqlstring ; // good for loop
> counters, like for($i=0;$i<something;$i++),parameters and retvals, to do
> not harmly interfere with function from we are called .it has opposite
> meaning to "globals"
>
> $caller_name=get_var_scope(); // we need to know from where we are called
> do construct error messages
>
> if ($database=="postgres")
> {
>
> // database postgres specific code
> $result=pg_exec($spojeni,$sqlstring);
> if ($result)
> {
> $lines=pg_numrows($result);
> if ($lines <1)
> {
> do something if we have no records. Typicaly display error message
> }
> if ($lines >1)
> {
> oops, database is inconsistent. Stop script
> die("database inconsistency in function." .$caller_name." contact
> server admin now")
> }
>
> if ($lines==1)
> {
> $retval= pg_fetch_array($result,0); // we have what we are looking
> for...
> }
>
> }
> else
> {
> die("No select from example_table in ".$caller_name)
> }
> }
>
> if ($database=="mysql")
> {
> // mysql specific code
>
> }
> etc etc etc.......
>
> return $retval;
>
>
> }
> ?>
>
>
> in the following example, simple and very "good readable" code is created,
> with is smaller, flexibile and simple to underestand and i expect, it will
> run faster.
>
> I thing, that my sugested langue extension can lead to more flexibile coding
> style, allow to bulid modular programs far better, increse readibility of
> php code and may lead to smaller and faster php programs in some very
> common situations. So may be useful to add it to php language.
>
>
> Abstract:
>
> Suggestion of adding capability "Explicit setting of variable scope inside
> user defined functions".
> adding "var_scope local", "var_scope global", and most useful "var_scope
> caller" to explicitly set, what variable scope will be used inside user
> defined function.Some supporting keywords and functions suggested too.
> keyword "local_vars variable list" as oposite for "globals" to avoid
> harm interference of private function varibles with variables of its
> caller and function "get_var_scope()" to detect, witch variable scope is
> currently used. I hope that this extension can lead to flexibile, shorter
> and faster PHP code in common situations and is "worth of implementation"
>
> Thanx for reading my letter and i appologize for wasting your time (if
> any).And execuse my bed english;
>
>
> NTPT
>
>
> ---
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> Zkontrolováno antivirovým systémem AVG (http://www.grisoft.cz).
> Verze: 6.0.401 / Virová báze: 226 - datum vydání: 9.10.2002
>
>
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