PHP Version 3.0 API Documentation

Table of Contents
-----------------
 1. Function Prototype
 2. Function Arguments
 3. Variable number of function arguments
 4. Using the function arguments
 5. Memory management in functions
 6. Setting variables in the symbol table
 7. Returning values from functions
 8. Returning 'complex' values from functions (arrays or objects)
 9. Using the resource list
10. Using the persistent resource table
11. Adding runtime configuration directives
----------------- 

1. Function Prototype

   All functions look like this:

       PHP_FUNCTION(foo) {

       }

   Even if your function doesn't take any arguments, this is how it is
   called.

-----------------

2. Function Arguments

   Arguments are always of type pval.  This type contains a union which
   has the actual type of the argument.  So, if your function takes two
   arguments, you would do something like the following at the top of your
   function:

       pval *arg1, *arg2;
       if (ARG_COUNT(ht) != 2 || getParameters(ht,2,&arg1,&arg2)==FAILURE) {
           WRONG_PARAM_COUNT;
       }

   NOTE: Arguments can be passed either by value or by reference. In both
   cases you will need to pass &(pval *) to getParameters. If you want to
   check if the n'th parameter was sent to you by reference or not, you can
   use the function, ParameterPassedByReference(ht,n). It will return either
   1 or 0.

   When you change any of the passed parameters, whether they are sent by
   reference or by value, you can either start over with the parameter by
   calling pval_destructor on it, or if it's an ARRAY you want to add to,
   you can use functions similar to the ones in internal_functions.h which
   manipulate return_value as an ARRAY.

   Also if you change a parameter to IS_STRING make sure you first assign
   the new estrdup'ed string and the string length, and only later change the
   type to IS_STRING. If you change the string of a parameter which already
   IS_STRING or IS_ARRAY you should run pval_destructor on it first.
   
-----------------

3. Variable number of function arguments

   A function can take a variable number of arguments.  If your function can
   take either 2 or 3 arguments, use the following:

       pval *arg1, *arg2, *arg3;
       int arg_count = ARG_COUNT(ht);

       if (arg_count<2 || arg_count>3 ||
           getParameters(ht,arg_count,&arg1,&arg2,&arg3)==FAILURE) {
           WRONG_PARAM_COUNT;
       }

------------------

4. Using the function arguments

   The type of each argument is stored in the pval type field:


   This type can be any of the following:

       IS_STRING             String
       IS_DOUBLE             Double-precision floating point
       IS_LONG               Long
       IS_ARRAY              Array

       IS_EMPTY              ??
       IS_USER_FUNCTION      ??
       IS_INTERNAL_FUNCTION  ?? (if some of these cannot be passed to a
                                 function - delete)
       IS_CLASS              ??
       IS_OBJECT             ??
       
   If you get an argument of one type and would like to use it as another,
   or if you just want to force the argument to be of a certain type, you
   can use one of the following conversion functions:

       convert_to_long(arg1);
       convert_to_double(arg1);
       convert_to_string(arg1); 
       convert_to_boolean_long(arg1);    If the string is "" or "0" it
                                         becomes 0, 1 otherwise
       convert_string_to_number(arg1);   Converts string to either LONG or
                                         DOUBLE depending on string

   These function all do in-place conversion.  They do not return anything.

   The actual argument is stored in a union.  

   For type IS_STRING, use arg1->value.str.val
            IS_LONG        arg1->value.lval
            IS_DOUBLE      arg1->value.dval
 
-------------------

5. Memory management in functions

   Any memory needed by a function should be allocated with either emalloc()
   or estrdup().  These are memory handling abstraction functions that look
   and smell like the normal malloc() and strdup() functions.  Memory should
   be freed with efree().

   There are two kinds of memory in this program. Memory which is returned
   to the parser in a variable and memory which you need for temporary
   storage in your internal function.  When you assign a string to a
   variable which is returned to the parser you need to make sure you first
   allocate the memory with either emalloc or estrdup.  This memory
   should NEVER be freed by you, unless you later, in the same function
   overwrite your original assignment (this kind of programming practice is
   not good though).

   For any temporary/permanent memory you need in your functions/library you
   should use the three emalloc(), estrdup(), and efree() functions. They
   behave EXACTLY like their counterpart functions. Anything you emalloc()
   or estrdup() you have to efree() at some point or another, unless it's
   supposed to stick around until the end of the program, otherwise there
   will be a memory leak. The meaning of "the functions behave exactly like
   their counterparts" is if you efree() something which was not
   emalloc()'ed nor estrdup()'ed you might get a segmentation fault. So
   please take care and free all of your wasted memory. One of the biggest
   improvements in PHP 3.0 will hopefully be the memory management.

   If you compile with "-DDEBUG", PHP3 will print out a list of all
   memory that was allocated using emalloc() and estrdup() but never
   freed with efree() when it is done running the specified script.

-------------------

6. Setting variables in the symbol table

   A number of macros are available which make it easier to set a variable
   in the symbol table:

       SET_VAR_STRING(name,value) **
       SET_VAR_DOUBLE(name,value)
       SET_VAR_LONG(name,value)

   ** Be careful here.  The value part must be malloc'ed manually because
      the memory management code will try to free this pointer later.  Do
      not pass statically allocated memory into a SET_VAR_STRING

  Symbol tables in PHP 3.0 are implemented as hash tables.  At any given time,
  &symbol_table is a pointer to the 'main' symbol table, and active_symbol_table
  points to the currently active symbol table (these may be identical like in
  startup, or different, if you're inside a function).
  
  The following examples use 'active_symbol_table'.  You should replace it with
  &symbol_table if you specifically want to work with the 'main' symbol table.
  Also, the same funcions may be applied to arrays, as explained below.
  
  * To check whether a variable named $foo already exists in a symbol table:
    if (hash_exists(active_symbol_table,"foo",sizeof("foo"))) { exists... }
    else { doesn't exist }
  
  * If you also need to get the type of the variable, you can use:
    hash_find(active_symbol_table,"foo",sizeof("foo"),&pvalue);
    check(pvalue.type);
  
  Arrays in PHP 3.0 are implemented using the same hashtables as symbol tables.
  This means the two above functions can also be used to check variables
  inside arrays.

  If you want to define a new array in a symbol table, you should do this:

      1.  Possibly check it exists and abort, using hash_exists()
          or hash_find().
      2.  Code:
  
      pval arr;
  
      if (array_init(&arr) == FAILURE) { failed... };
      hash_update(active_symbol_table,"foo",sizeof("foo"),&arr,sizeof(pval),NULL);
  
  This code declares a new array, named $foo, in the active symbol table.
  This array is empty.
  
  Here's how to add new entries to it:
  
      pval entry;
  
      entry.type = IS_LONG;
      entry.value.lval = 5;
  
      hash_update(arr.value.ht,"bar",sizeof("bar"),&entry,sizeof(pval),NULL); /* defines $foo["bar"] = 5 */
      hash_index_update(arr.value.ht,7,&entry,sizeof(pval),NULL); /* defines $foo[7] = 5 */
      hash_next_index_insert(arr.value.ht,&entry,sizeof(pval),NULL); /* defines the next free place in $foo[],
                                                                         * $foo[8], to be 5 (works like php2)
                                                                         */
  
  If you'd like to modify a value that you inserted to a hash, you must first retreive it from the hash.  To
  prevent that overhead, you can supply a pval ** to the hash add function, and it'll be updated with the
  pval * address of the inserted element inside the hash.  If that value is NULL (like in all of the
  above examples) - that parameter is ignored.

  hash_next_index_insert() works more or less using the same logic
  "$foo[] = bar;" works in PHP 2.0.

  If you are building an array to return from a function, you can initialize
  the array just like above by doing:

    if (array_init(return_value) == FAILURE) { failed...; }

  and then adding values with the helper functions:

    add_next_index_long(return_value,long_value);
    add_next_index_double(return_value,double_value);
    add_next_index_string(return_value,estrdup(string_value));
  
  Of course, if the adding isn't done right after the array
  initialization, you'd probably have to look for the array first:
  
    pval *arr;
  
    if (hash_find(active_symbol_table,"foo",sizeof("foo"),(void **)&arr)==FAILURE) { can't find... }
    else { use arr->value.ht... }
  
  Note that hash_find receives a pointer to a pval pointer, and
  not a pval pointer.
  
  Just about any hash function returns SUCCESS or FAILURE (except for
  hash_exists() that returns a boolean truth value).
    
-------------------

7. Returning 'simple' values from functions (integers, floats or strings)

   A number of macros are available to make it easier to return things from
   functions:

   These set the return value and return from the function:

   RETURN_FALSE
   RETURN_TRUE
   RETURN_LONG(l)
   RETURN_STRING(s,dup)        If dup is true, duplicates the string
   RETURN_STRINGL(s,l,dup)     Return string (s) specifying length (l).
   RETURN_DOUBLE(d)

   These only set the return value:

   RETVAL_FALSE
   RETVAL_TRUE
   RETVAL_LONG(l)
   RETVAL_STRING(s,dup)       If dup is true, duplicates the string
   RETVAL_STRINGL(s,l,dup)    Return string (s) specifying length (l).
   RETVAL_DOUBLE(d)

   The string macros above will all estrdup() the passed 's' argument,
   so you can safely free the argument after calling the macro, or
   alternatively use statically allocated memory.

   If your function returns boolean success/error responses, always use
   RETURN_TRUE and RETURN_FALSE respectively.

-------------------

8. Returning 'complex' values from functions (arrays or objects)

   Your function can also return a complex data type such as an object
   or an array.

   Returning an object:

   1. Call object_init(return_value).
   2. Fill it up with values:

   add_property_long(return_value,property_name,l)			Add a property named 'property_name', of type long, equals to 'l'
   add_property_double(return_value,property_name,d)		Same, only a double
   add_property_string(return_value,property_name,str)		Same, only a string
   add_property_stringl(return_value,property_name,str,l)	Add a property named 'property_name', of type string, string is 'str' with length 'l'

   3. Possibly, register functions for this object.  In order to
      obtain values from the object, the function would have to fetch
      "this" from the active_symbol_table.  Its type should be IS_OBJECT,
      and it's basically a regular hash table (i.e., you can use regular
      hash functions on .value.ht).  The actual registration of the
      function can be done using:
   
   add_method(return_value,function_name,function_ptr)
   
   
   Returning an array:

   1.  Call array_init(return_value).
   2.  Fill it up with values:

   add_assoc_long(return_value,key,l)				add associative entry with key 'key' and long value 'l'
   add_assoc_double(return_value,key,d)		
   add_assoc_string(return_value,key,str)
   add_assoc_stringl(return_value,key,str,length)	specify the string length

   add_index_long(return_value,index,l)				add entry in index 'index' with long value 'l'
   add_index_double(return_value,index,d)
   add_index_string(return_value,index,str)
   add_index_stringl(return_value,index,str,length)  specify the string length

   add_next_index_long(return_value,l)				add an array entry in the next free offset with long value 'l'
   add_next_index_double(return_value,d)
   add_next_index_string(return_value,str)
   add_next_index_stringl(return_value,str,length)	specify the string length

-------------------

9. Using the resource list

   PHP 3.0 has a standard way of dealing with various types of resources,
   that replaces all of the local linked lists in PHP 2.0.

   Available functions:

   php3_list_insert(ptr, type)      returns the 'id' of the newly inserted resource
   php3_list_delete(id)             delete the resource with the specified id
   php3_list_find(id,*type)         returns the pointer of the resource with the specified id, updates 'type' to the resource's type

   Typically, these functions are used for SQL drivers but they can be
   used for anything else, and are used, for instance, for maintaining
   file descriptors.

   Typical list code would look like this:

	Adding a new resource:

		RESOURCE *resource;

		...allocate memory for resource and acquire resource...
		/* add a new resource to the list */
		return_value->value.lval = php3_list_insert((void *) resource, LE_RESOURCE_TYPE);
		return_value->type = IS_LONG;

	Using an existing resource:

		pval *resource_id;
		RESOURCE *resource;
		int type;

		convert_to_long(resource_id);
		resource = php3_list_find(resource_id->value.lval, &type);
		if (type != LE_RESOURCE_TYPE) {
			php3_error(E_WARNING,"resource index %d has the wrong type",resource_id->value.lval);
			RETURN_FALSE;
		}
		...use resource...

	Deleting an existing resource:

		pval *resource_id;
		RESOURCE *resource;
		int type;

		convert_to_long(resource_id);
		php3_list_delete(resource_id->value.lval);
   

   The resource types should be registered in php3_list.h, in enum
   list_entry_type.  In addition, one should add shutdown code for any
   new resource type defined, in list.c's list_entry_destructor() (even if
   you don't have anything to do on shutdown, you must add an empty case).

-------------------

10. Using the persistent resource table

   PHP 3.0 has a standard way of storing persistent resources (i.e.,
   resources that are kept in between hits).  The first module to use
   this feature was the MySQL module, and mSQL followed it, so one can
   get the general impression of how a persistent resource should be
   used by reading mysql.c.  The functions you should look at are:
   php3_mysql_do_connect()
   php3_mysql_connect()
   php3_mysql_pconnect()

   The general idea of persistence modules is this:
   1.  Code all of your module to work with the regular resource list
       mentioned in section (9).
   2.  Code extra connect functions that check if the resource already
       exists in the persistent resource list.  If it does, register it
       as in the regular resource list as a pointer to the persistent
       resource list (because of 1., the rest of the code
       should work immediately).  If it doesn't, then create it, add it
       to the persistent resource list AND add a pointer to it from the
       regular resource list, so all of the code would work since it's
       in the regular resource list, but on the next connect, the
       resource would be found in the persistent resource list and be
       used without having to recreate it.
       You should register these resources with a different type (e.g.
       LE_MYSQL_LINK for non-persistent link and LE_MYSQL_PLINK for
       a persistent link).

   If you read mysql.c, you'll notice that except for the more complex
   connect function, nothing in the rest of the module has to be changed.
   
   The very same interface exists for the regular resource list and the
   persistent resource list, only 'list' is replaced with 'plist':

   php3_plist_insert(ptr, type)      returns the 'id' of the newly inserted resource
   php3_plist_delete(id)             delete the resource with the specified id
   php3_plist_find(id,*type)         returns the pointer of the resource with the specified id, updates 'type' to the resource's type

   However, it's more than likely that these functions would prove
   to be useless for you when trying to implement a persistent module.
   Typically, one would want to use the fact that the persistent resource
   list is really a hash table.  For instance, in the MySQL/mSQL modules,
   when there's a pconnect() call (persistent connect), the function
   builds a string out of the host/user/passwd that were passed to the
   function, and hashes the SQL link with this string as a key.  The next
   time someone calls a pconnect() with the same host/user/passwd, the
   same key would be generated, and the function would find the SQL link
   in the persistent list.

   Until further documented, you should look at mysql.c or msql.c to
   see how one should use the plist's hash table abilities.

   One important thing to note:  resources going into the persistent
   resource list must *NOT* be allocated with PHP's memory manager, i.e.,
   they should NOT be created with emalloc(), estrdup(), etc.  Rather,
   one should use the regular malloc(), strdup(), etc.  The reason for
   this is simple - at the end of the request (end of the hit), every
   memory chunk that was allocated using PHP's memory manager is deleted.
   Since the persistent list isn't supposed to be erased at the end
   of a request, one mustn't use PHP's memory manager for allocating
   resources that go to it.

   Shutting down persistent resources:  
   
   When you register resource that's going to be in the persistent list,
   you should add destructors to it both in the non-persistent list
   and in the persistent list.
   The destructor in the non-persistent list destructor shouldn't do anything.
   The one in the persistent list destructor should properly free any
   resources obtained by that type (e.g. memory, SQL links, etc).  Just like
   with the non-persistent resources, you *MUST* add destructors for every
   resource, even it requires no destructotion and the destructor would
   be empty.
   Remember, since emalloc() and friends aren't to be used in conjunction
   with the persistent list, you mustn't use efree() here either.

-------------------

11. Adding runtime configuration directives

Many of the features of PHP3 can be configured at runtime.  These
configuration directives can appear in either the designated php3.ini
file, or in the case of the Apache module version in the Apache .conf
files.  The advantage of having them in the Apache .conf files is that
they can be configured on a per-directory basis.  This means that one
directory may have a certain safemodeexecdir for example, while another
directory may have another.  This configuration granularity is especially
handy when a server supports multiple virtual hosts.

The steps required to add a new directive:

 1. Add directive to php3_ini_structure struct in mod_php4.h. 
    
 2. In main.c, edit the php3_module_startup function and add the
    appropriate cfg_get_string() or cfg_get_long() call.

 3. Add the directive, restrictions and a comment to the php3_commands
    structure in mod_php4.c.  Note the restrictions part.  RSRC_CONF are
    directives that can only be present in the actual Apache .conf files.
    Any OR_OPTIONS directives can be present anywhere, include normal
    .htaccess files.

 4. In either php3take1handler() or php3flaghandler() add the appropriate
    entry for your directive.

 5. In the configuration section of the _php3_info() function in
    functions/info.c you need to add your new directive.

 6. And last, you of course have to use your new directive somewhere.
    It will be addressable as php3_ini.directive
