php-doc-en/reference/mysqli/functions/mysqli-change-user.xml

<?xml version="1.0" encoding="iso-8859-1"?>
<!-- $Revision: 1.12 $ -->
  <refentry id="function.mysqli-change-user">
   <refnamediv>
    <refname>mysqli_change_user</refname>
    <refname>mysqli->change_user</refname>
    <refpurpose>Changes the user of the specified database connection</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
    <para>Procedural style:</para>
    <methodsynopsis>
     <type>bool</type><methodname>mysqli_change_user</methodname>
     <methodparam><type>object</type><parameter>link</parameter></methodparam>
     <methodparam><type>string</type><parameter>user</parameter></methodparam>
     <methodparam><type>string</type><parameter>password</parameter></methodparam>
     <methodparam><type>string</type><parameter>database</parameter></methodparam>
    </methodsynopsis>
    <para>Object oriented style (method):</para>
    <classsynopsis>
     <ooclass><classname>mysqli</classname></ooclass>
     <methodsynopsis>
      <type>bool</type>
      <methodname>change_user</methodname>
      <methodparam><type>string</type><parameter>user</parameter></methodparam>
      <methodparam><type>string</type><parameter>password</parameter></methodparam>
      <methodparam><type>string</type><parameter>database</parameter></methodparam>
     </methodsynopsis>
    </classsynopsis>     
    <para>
     <function>mysqli_change_user</function> is used to change the user of the specified
     database connection as given by the <parameter>link</parameter> parameter and to set the 
     current database to that specified by the <parameter>database</parameter> parameter. 
    </para>
    <para>
     If desired, the &null; value may be passed in place of the <parameter>database</parameter>
     parameter resulting in only changing the user and not selecting a database. To select
     a database in this case use the <function>mysqli_select_db</function> function.
    </para>
    <para>
     In order to successfully change users a valid <parameter>username</parameter> and
     <parameter>password</parameter> parameters must be provided and that user must have
     sufficient permissions to access the desired database. If for any reason authorization
     fails, the current user authentication will remain.
    </para>
    <note>
     <para>
      Using this command will always cause the current database connection to behave as if
      was a completely new database connection, regardless of if the operation was completed
      successfully. This reset includes performing a rollback on any active transactions, 
      closing all temporary tables, and unlocking all locked tables.
     </para>
    </note>
   </refsect1>
   <refsect1>
    <title>Return Values</title>
    <para>
     &return.success;
    </para>
   </refsect1>
   <refsect1>
    <title>See also:</title>
    <para>
     <function>mysqli_connect</function>
     <function>mysqli_select_db</function>
    </para>
   </refsect1>
   <refsect1>
    <title>Example</title>
     <example>
      <title>Object oriented style</title>
      <programlisting role="php">
<![CDATA[
<?php

/* connect database test */
$mysqli = new mysqli("localhost", "my_user", "my_password", "test");

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

/* Set Variable a */
$mysqli->query("SET @a:=1");
                                         
/* reset all and select a new database */
$mysqli->change_user("my_user", "my_password", "world");

if ($result = $mysqli->query("SELECT DATABASE()")) {
    $row = $result->fetch_row();
    printf("Default database: %s\n", $row[0]);
    $result->close();
}

if ($result = $mysqli->query("SELECT @a")) {
    $row = $result->fetch_row();
    if ($row[0] === NULL) {
        printf("Value of variable a is NULL\n");
    }
    $result->close();
}

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

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

/* Set Variable a */
mysqli_query($link, "SET @a:=1");
                                         
/* reset all and select a new database */
mysqli_change_user($link, "my_user", "my_password", "world");

if ($result = mysqli_query($link, "SELECT DATABASE()")) {
    $row = mysqli_fetch_row($result);
    printf("Default database: %s\n", $row[0]);
    mysqli_free_result($result);
}

if ($result = mysqli_query($link, "SELECT @a")) {
    $row = mysqli_fetch_row($result);
    if ($row[0] === NULL) {
        printf("Value of variable a is NULL\n");
    }
    mysqli_free_result($result);
}

/* close connection */
mysqli_close($link);
?>
]]>
     </programlisting>
    </example>
    <para>
     The above examples would produce the following output:
    </para>
    <screen>
<![CDATA[
Default database: world
Value of variable a is NULL
]]>
    </screen>
   </refsect1>
  </refentry>

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