php-doc-en/reference/mysqli/functions/mysqli-prepare.xml

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  <refentry id="function.mysqli-prepare">
   <refnamediv>
    <refname>mysqli_prepare</refname>
    <refname>mysqli->prepare</refname>
    <refpurpose>
     Prepare a SQL statement for execution
    </refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <para>Procedure style:</para>
     <methodsynopsis>
      <type>mysqli_stmt</type><methodname>mysqli_prepare</methodname>
      <methodparam><type>mysqli</type><parameter>link</parameter></methodparam>
      <methodparam><type>string</type><parameter>query</parameter></methodparam>
     </methodsynopsis>
    <para>Object oriented style (method)</para>
     <classsynopsis>
      <ooclass><classname>mysqli</classname></ooclass>
      <methodsynopsis>
       <type>mysqli_stmt</type><methodname>prepare</methodname>
       <methodparam><type>string</type><parameter>query</parameter></methodparam>
      </methodsynopsis>
     </classsynopsis>
     <para>
      <function>mysqli_prepare</function> prepares the SQL query pointed to by the
      null-terminated string query, and returns a statement handle to be used for 
      further operations on the statement. The query must consist of a single SQL statement.
     </para>
     <note>
      <para>
       You should not add a terminating semicolon or <literal>\g</literal>
       to the statement.
      </para>
     </note>
     <para>
      The parameter <parameter>query</parameter>  can include one or more parameter markers 
      in the SQL statement by embedding question mark (<literal>?</literal>) characters
      at the appropriate positions. 
     </para>
     <note>
      <para>
       The markers are legal only in certain places in SQL statements. 
       For example, they are allowed in the VALUES() list of an INSERT statement
       (to specify column values for a row), or in a comparison with a column in 
       a WHERE clause to specify a comparison value. 
      </para>
      <para>
       However, they are not allowed for identifiers (such as table or column names),
       in the select list that names the columns to be returned by a SELECT statement,
       or to specify both operands of a binary operator such as the <literal>=</literal>
       equal sign. The latter restriction is necessary because it would be impossible
       to determine the parameter type. It's not allowed to compare marker
       with <literal>NULL</literal> by <literal>? IS NULL</literal> too.
       In general, parameters are legal only in Data
       Manipulation Languange (DML) statements, and not in Data Defination Language
       (DDL) statements. 
      </para>
     </note>
     <para>
      The parameter markers must be bound to application variables using 
      <function>mysqli_stmt_bind_param</function> and/or <function>mysqli_stmt_bind_result</function>
      before executing the statement or fetching rows. 
     </para>
   </refsect1>
   <refsect1>
    &reftitle.returnvalues;
    <para>
     <function>mysqli_prepare</function> returns a statement object or &false; if an error occured.
    </para>
   </refsect1>
   <refsect1>
    &reftitle.seealso;
    <para>
     <function>mysqli_stmt_execute</function>,
     <function>mysqli_stmt_fetch</function>,
     <function>mysqli_stmt_bind_param</function>,
     <function>mysqli_stmt_bind_result</function>&listendand;
     <function>mysqli_stmt_close</function>.
    </para>
   </refsect1>
   <refsect1>
    &reftitle.examples;
    <example>
     <title>Object oriented style</title>
     <programlisting role="php">
<![CDATA[
<?php
$mysqli = new mysqli("localhost", "my_user", "my_password", "world");

/* check connection */
if (mysqli_connect_errno()) {
    printf("Connect failed: %s\n", mysqli_connect_error());
    exit();
}

$city = "Amersfoort";

/* create a prepared statement */
if ($stmt = $mysqli->prepare("SELECT District FROM City WHERE Name=?")) {

    /* bind parameters for markers */
    $stmt->bind_param("s", $city);

    /* execute query */
    $stmt->execute();

    /* bind result variables */
    $stmt->bind_result($district);

    /* fetch value */
    $stmt->fetch();

    printf("%s is in district %s\n", $city, $district);

    /* close statement */
    $stmt->close();
} 

/* close connection */
$mysqli->close();
?>
]]>
    </programlisting>
    </example>
    <example>
     <title>Procedural style</title>
     <programlisting role="php">
<![CDATA[
<?php
$link = mysqli_connect("localhost", "my_user", "my_password", "world");

/* check connection */
if (mysqli_connect_errno()) {
    printf("Connect failed: %s\n", mysqli_connect_error());
    exit();
}

$city = "Amersfoort";

/* create a prepared statement */
if ($stmt = mysqli_prepare($link, "SELECT District FROM City WHERE Name=?")) {

    /* bind parameters for markers */
    mysqli_stmt_bind_param($stmt, "s", $city);

    /* execute query */
    mysqli_stmt_execute($stmt);

    /* bind result variables */
    mysqli_stmt_bind_result($stmt, $district);

    /* fetch value */
    mysqli_stmt_fetch($stmt);

    printf("%s is in district %s\n", $city, $district);

    /* close statement */
    mysqli_stmt_close($stmt);
} 

/* close connection */
mysqli_close($link);
?>
]]>
     </programlisting>
    </example>
    &example.outputs;
    <screen>
<![CDATA[
Amersfoort is in district Utrecht
]]>
    </screen>
   </refsect1>
  </refentry>

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