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<?xml version="1.0" encoding="iso-8859-1"?>
<!-- $Revision: 1.2 $ -->
<sect1 xml:id="internals2.pdo.pdo_stmt_t" xmlns="http://docbook.org/ns/docbook">
<title>pdo_stmt_t definition</title>
<para>
All fields should be treated as read-only unless explicitly stated
otherwise.
</para>
<figure>
<title>pdo_stmt_t</title>
<programlisting role="c">
/* represents a prepared statement */
struct _pdo_stmt_t {
/* driver specifics */
struct pdo_stmt_methods *methods; <co xml:id="internals2.pdo.stmt.co.methods" linkends="internals2.pdo.stmt.co.methods-co"/>
void *driver_data; <co
xml:id="internals2.pdo.stmt.co.driver-data"
linkends="internals2.pdo.stmt.co.driver-data-co"/>
/* if true, we've already successfully executed this statement at least
* once */
unsigned executed:1; <co
xml:id="internals2.pdo.stmt.co.executed"
linkends="internals2.pdo.stmt.co.executed-co"/>
/* if true, the statement supports placeholders and can implement
* bindParam() for its prepared statements, if false, PDO should
* emulate prepare and bind on its behalf */
unsigned supports_placeholders:2; <co xml:id="internals2.pdo.stmt.co.holder"
linkends="internals2.pdo.stmt.co.holder-co"/>
/* the number of columns in the result set; not valid until after
* the statement has been executed at least once. In some cases, might
* not be valid until fetch (at the driver level) has been called at least once.
* */
int column_count; <co
xml:id="internals2.pdo.stmt.co.colcount"
linkends="internals2.pdo.stmt.co.colcount-co"/>
struct pdo_column_data *columns; <co
xml:id="internals2.pdo.stmt.co.cols" linkends="internals2.pdo.stmt.co.cols-co"/>
/* points at the dbh that this statement was prepared on */
pdo_dbh_t *dbh;
/* keep track of bound input parameters. Some drivers support
* input/output parameters, but you can't rely on that working */
HashTable *bound_params;
/* When rewriting from named to positional, this maps positions to names */
HashTable *bound_param_map;
/* keep track of PHP variables bound to named (or positional) columns
* in the result set */
HashTable *bound_columns;
/* not always meaningful */
long row_count;
/* used to hold the statement's current query */
char *query_string;
int query_stringlen;
/* the copy of the query with expanded binds ONLY for emulated-prepare drivers */
char *active_query_string;
int active_query_stringlen;
/* the cursor specific error code. */
pdo_error_type error_code;
/* used by the query parser for driver specific
* parameter naming (see pgsql driver for example) */
const char *named_rewrite_template;
};
</programlisting>
</figure>
<calloutlist>
<callout xml:id="internals2.pdo.stmt.co.methods-co"
arearefs="internals2.pdo.stmt.co.methods">
<para>
The driver <emphasis>must</emphasis> set this during
<function>SKEL_handle_preparer</function>.
</para>
</callout>
<callout arearefs="internals2.pdo.stmt.co.driver-data"
xml:id="internals2.pdo.stmt.co.driver-data-co">
<para>
This item is for use by the driver; the intended usage is to store a
pointer (during <function>SKEL_handle_factory</function>)
to whatever instance data is required to maintain a connection to
the database.
</para>
</callout>
<callout arearefs="internals2.pdo.stmt.co.executed"
xml:id="internals2.pdo.stmt.co.executed-co">
<para>
This is set by PDO after the statement has been executed for the first
time. Your driver can inspect this value to determine if it can skip
one-time actions as an optimization.
</para>
</callout>
<callout arearefs="internals2.pdo.stmt.co.holder"
xml:id="internals2.pdo.stmt.co.holder-co">
<para>
Discussed in more detail in <xref linkend="internals2.pdo.preparer"/>.
</para>
</callout>
<callout arearefs="internals2.pdo.stmt.co.colcount"
xml:id="internals2.pdo.stmt.co.colcount-co">
<para>
Your driver is responsible for setting this field to the number of
columns available in a result set. This is usually set during
<function>SKEL_stmt_execute</function> but with some database
implementations, the column count may not be available until
<function>SKEL_stmt_fetch</function> has been called at least once.
Drivers that implement <function>SKEL_stmt_next_rowset</function> should
update the column count when a new rowset is available.
</para>
</callout>
<callout arearefs="internals2.pdo.stmt.co.cols"
xml:id="internals2.pdo.stmt.co.cols-co">
<para>
PDO will allocate this field based on the value that you set for the
column count. You are responsible for populating each column during
<function>SKEL_stmt_describe</function>. You must set the
<parameter>precision</parameter>, <parameter>maxlen</parameter>,
<parameter>name</parameter>, <parameter>namelen</parameter> and
<parameter>param_type</parameter> members for each column.
The <parameter>name</parameter> is expected to be allocated using
<function>emalloc</function>; PDO will call <function>efree</function> at
the appropriate time.
</para>
</callout>
</calloutlist>
</sect1>
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