fetch.xml

<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->
<refentry xml:id="pdostatement.fetch" xmlns="http://docbook.org/ns/docbook">
 <refnamediv>
  <refname>PDOStatement::fetch</refname>
  <refpurpose>
   Fetches the next row from a result set
  </refpurpose>
 </refnamediv>
 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis role="PDOStatement">
   <modifier>public</modifier> <type>mixed</type><methodname>PDOStatement::fetch</methodname>
   <methodparam choice="opt"><type>int</type><parameter>mode</parameter><initializer>PDO::FETCH_DEFAULT</initializer></methodparam>
   <methodparam choice="opt"><type>int</type><parameter>cursorOrientation</parameter><initializer>PDO::FETCH_ORI_NEXT</initializer></methodparam>
   <methodparam choice="opt"><type>int</type><parameter>cursorOffset</parameter><initializer>0</initializer></methodparam>
  </methodsynopsis>

  <para>
   Fetches a row from a result set associated with a PDOStatement object. The
   <parameter>mode</parameter> parameter determines how PDO returns
   the row.
  </para>
 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>mode</parameter></term>
     <listitem>
      <para>
       Controls how the next row will be returned to the caller. This value
       must be one of the <literal>PDO::FETCH_*</literal> constants,
       defaulting to value of <literal>PDO::ATTR_DEFAULT_FETCH_MODE</literal>
       (which defaults to <literal>PDO::FETCH_BOTH</literal>).
       <itemizedlist>
        <listitem><para>
         <literal>PDO::FETCH_ASSOC</literal>: returns an array indexed by column
         name as returned in your result set
        </para></listitem>
        <listitem><para>
         <literal>PDO::FETCH_BOTH</literal> (default): returns an array indexed by
         both column name and 0-indexed column number as returned in your
         result set
        </para></listitem>
        <listitem><para>
         <literal>PDO::FETCH_BOUND</literal>: returns &true; and assigns the
         values of the columns in your result set to the PHP variables to which
         they were bound with the <methodname>PDOStatement::bindColumn</methodname>
         method
        </para></listitem>
        <listitem><para>
         <literal>PDO::FETCH_CLASS</literal>: returns a new instance of the
         requested class, mapping the columns of the result set to named
         properties in the class, and calling the constructor afterwards, unless
         <literal>PDO::FETCH_PROPS_LATE</literal> is also given.
         If <parameter>mode</parameter>
         includes PDO::FETCH_CLASSTYPE (e.g. <literal>PDO::FETCH_CLASS |
         PDO::FETCH_CLASSTYPE</literal>) then the name of the class is
         determined from a value of the first column.
        </para></listitem>
        <listitem><para>
         <literal>PDO::FETCH_INTO</literal>: updates an existing instance
         of the requested class, mapping the columns of the result set to
         named properties in the class
        </para></listitem>
        <listitem><para>
         <literal>PDO::FETCH_LAZY</literal>: combines
         <literal>PDO::FETCH_BOTH</literal> and <literal>PDO::FETCH_OBJ</literal>,
         creating the object variable names as they are accessed
        </para></listitem>
        <listitem><para>
         <literal>PDO::FETCH_NAMED</literal>: returns an array with the same
         form as <literal>PDO::FETCH_ASSOC</literal>, except that if there are
         multiple columns with the same name, the value referred to by that
         key will be an array of all the values in the row that had that
         column name
        </para></listitem>
        <listitem><para>
         <literal>PDO::FETCH_NUM</literal>: returns an array indexed by column
         number as returned in your result set, starting at column 0
        </para></listitem>
        <listitem><para>
         <literal>PDO::FETCH_OBJ</literal>: returns an anonymous object with
         property names that correspond to the column names returned in your
         result set
        </para></listitem>
        <listitem><para>
         <literal>PDO::FETCH_PROPS_LATE</literal>: when used with
         <literal>PDO::FETCH_CLASS</literal>, the constructor of the class is
         called before the properties are assigned from the respective column
         values.
        </para></listitem>
       </itemizedlist>
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>cursorOrientation</parameter></term>
     <listitem>
      <para>
       For a PDOStatement object representing a scrollable cursor, this
       value determines which row will be returned to the caller. This value
       must be one of the <literal>PDO::FETCH_ORI_*</literal> constants,
       defaulting to <literal>PDO::FETCH_ORI_NEXT</literal>. To request a
       scrollable cursor for your PDOStatement object, you must set the
       <literal>PDO::ATTR_CURSOR</literal> attribute to
       <literal>PDO::CURSOR_SCROLL</literal> when you prepare the SQL
       statement with <methodname>PDO::prepare</methodname>.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>cursorOffset</parameter></term>
     <listitem>
      <para> 
       For a PDOStatement object representing a scrollable cursor for which
       the <parameter>cursorOrientation</parameter> parameter is set to
       <literal>PDO::FETCH_ORI_ABS</literal>, this value specifies the
       absolute number of the row in the result set that shall be fetched.
      </para>
      <para>
       For a PDOStatement object representing a scrollable cursor for which
       the <parameter>cursorOrientation</parameter> parameter is set to
       <literal>PDO::FETCH_ORI_REL</literal>, this value specifies the
       row to fetch relative to the cursor position before
       <methodname>PDOStatement::fetch</methodname> was called.
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>

 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   The return value of this function on success depends on the fetch type. In
   all cases, &false; is returned on failure or if there are no more rows.
  </para>
 </refsect1>

 <refsect1 role="errors">
  &reftitle.errors;
  &pdo.errors;
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example><title>Fetching rows using different fetch styles</title>
    <programlisting role="php">
<![CDATA[
<?php
$sth = $dbh->prepare("SELECT name, colour FROM fruit");
$sth->execute();

/* Exercise PDOStatement::fetch styles */
print("PDO::FETCH_ASSOC: ");
print("Return next row as an array indexed by column name\n");
$result = $sth->fetch(PDO::FETCH_ASSOC);
print_r($result);
print("\n");

print("PDO::FETCH_BOTH: ");
print("Return next row as an array indexed by both column name and number\n");
$result = $sth->fetch(PDO::FETCH_BOTH);
print_r($result);
print("\n");

print("PDO::FETCH_LAZY: ");
print("Return next row as an anonymous object with column names as properties\n");
$result = $sth->fetch(PDO::FETCH_LAZY);
print_r($result);
print("\n");

print("PDO::FETCH_OBJ: ");
print("Return next row as an anonymous object with column names as properties\n");
$result = $sth->fetch(PDO::FETCH_OBJ);
print $result->name;
print("\n");
?>
]]>
    </programlisting>
    &example.outputs;
    <screen>
<![CDATA[
PDO::FETCH_ASSOC: Return next row as an array indexed by column name
Array
(
    [name] => apple
    [colour] => red
)

PDO::FETCH_BOTH: Return next row as an array indexed by both column name and number
Array
(
    [name] => banana
    [0] => banana
    [colour] => yellow
    [1] => yellow
)

PDO::FETCH_LAZY: Return next row as an anonymous object with column names as properties
PDORow Object
(
    [name] => orange
    [colour] => orange
)

PDO::FETCH_OBJ: Return next row as an anonymous object with column names as properties
kiwi
]]>
    </screen>
   </example>
   <example><title>Fetching rows with a scrollable cursor</title>
    <programlisting role="php">
<![CDATA[
<?php
function readDataForwards($dbh) {
    $sql = 'SELECT hand, won, bet FROM mynumbers ORDER BY BET';
    $stmt = $dbh->prepare($sql, array(PDO::ATTR_CURSOR => PDO::CURSOR_SCROLL));
    $stmt->execute();
    while ($row = $stmt->fetch(PDO::FETCH_NUM, PDO::FETCH_ORI_NEXT)) {
        $data = $row[0] . "\t" . $row[1] . "\t" . $row[2] . "\n";
        print $data;
    }
}
function readDataBackwards($dbh) {
    $sql = 'SELECT hand, won, bet FROM mynumbers ORDER BY bet';
    $stmt = $dbh->prepare($sql, array(PDO::ATTR_CURSOR => PDO::CURSOR_SCROLL));
    $stmt->execute();
    $row = $stmt->fetch(PDO::FETCH_NUM, PDO::FETCH_ORI_LAST);
    do {
        $data = $row[0] . "\t" . $row[1] . "\t" . $row[2] . "\n";
        print $data;
    } while ($row = $stmt->fetch(PDO::FETCH_NUM, PDO::FETCH_ORI_PRIOR));
}

print "Reading forwards:\n";
readDataForwards($conn);

print "Reading backwards:\n";
readDataBackwards($conn);
?>
]]>
    </programlisting>
    &example.outputs;
    <screen>
<![CDATA[
Reading forwards:
21    10    5
16    0     5
19    20    10

Reading backwards:
19    20    10
16    0     5
21    10    5
]]>
    </screen>
   </example>

   <example><title>Construction order</title>
    <simpara>
     When objects are fetched via <literal>PDO::FETCH_CLASS</literal> the object
     properties are assigned first, and then the constructor of the class is
     invoked. If <literal>PDO::FETCH_PROPS_LATE</literal> is also given, this
     order is reversed, i.e. first the constructor is called, and afterwards the
     properties are assigned.
    </simpara>
    <programlisting role="php">
<![CDATA[
<?php
class Person
{
    private $name;

    public function __construct()
    {
        $this->tell();
    }

    public function tell()
    {
        if (isset($this->name)) {
            echo "I am {$this->name}.\n";
        } else {
            echo "I don't have a name yet.\n";
        }
    }
}

$sth = $dbh->query("SELECT * FROM people");
$sth->setFetchMode(PDO::FETCH_CLASS, 'Person');
$person = $sth->fetch();
$person->tell();
$sth->setFetchMode(PDO::FETCH_CLASS|PDO::FETCH_PROPS_LATE, 'Person');
$person = $sth->fetch();
$person->tell();
?>
]]>
    </programlisting>
    &example.outputs.similar;
    <screen>
<![CDATA[
I am Alice.
I am Alice.
I don't have a name yet.
I am Bob.
]]>
    </screen>
   </example>
  </para>
 </refsect1>

 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><methodname>PDO::prepare</methodname></member>
    <member><methodname>PDOStatement::execute</methodname></member>
    <member><methodname>PDOStatement::fetchAll</methodname></member>
    <member><methodname>PDOStatement::fetchColumn</methodname></member>
    <member><methodname>PDOStatement::fetchObject</methodname></member>
    <member><methodname>PDOStatement::setFetchMode</methodname></member>
   </simplelist>
  </para>
 </refsect1>
</refentry>
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