Файл: CodeIgniter-3.0.3/user_guide/database/connecting.html
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<div class="section" id="connecting-to-your-database">
<h1>Connecting to your Database<a class="headerlink" href="#connecting-to-your-database" title="Permalink to this headline">¶</a></h1>
<p>There are two ways to connect to a database:</p>
<div class="section" id="automatically-connecting">
<h2>Automatically Connecting<a class="headerlink" href="#automatically-connecting" title="Permalink to this headline">¶</a></h2>
<p>The “auto connect” feature will load and instantiate the database class
with every page load. To enable “auto connecting”, add the word database
to the library array, as indicated in the following file:</p>
<p>application/config/autoload.php</p>
</div>
<div class="section" id="manually-connecting">
<h2>Manually Connecting<a class="headerlink" href="#manually-connecting" title="Permalink to this headline">¶</a></h2>
<p>If only some of your pages require database connectivity you can
manually connect to your database by adding this line of code in any
function where it is needed, or in your class constructor to make the
database available globally in that class.</p>
<div class="highlight-ci"><div class="highlight"><pre><span class="nv">$this</span><span class="o">-></span><span class="na">load</span><span class="o">-></span><span class="na">database</span><span class="p">();</span>
</pre></div>
</div>
<p>If the above function does <strong>not</strong> contain any information in the first
parameter it will connect to the group specified in your database config
file. For most people, this is the preferred method of use.</p>
<div class="section" id="available-parameters">
<h3>Available Parameters<a class="headerlink" href="#available-parameters" title="Permalink to this headline">¶</a></h3>
<ol class="arabic simple">
<li>The database connection values, passed either as an array or a DSN
string.</li>
<li>TRUE/FALSE (boolean). Whether to return the connection ID (see
Connecting to Multiple Databases below).</li>
<li>TRUE/FALSE (boolean). Whether to enable the Query Builder class. Set
to TRUE by default.</li>
</ol>
</div>
<div class="section" id="manually-connecting-to-a-database">
<h3>Manually Connecting to a Database<a class="headerlink" href="#manually-connecting-to-a-database" title="Permalink to this headline">¶</a></h3>
<p>The first parameter of this function can <strong>optionally</strong> be used to
specify a particular database group from your config file, or you can
even submit connection values for a database that is not specified in
your config file. Examples:</p>
<p>To choose a specific group from your config file you can do this:</p>
<div class="highlight-ci"><div class="highlight"><pre><span class="nv">$this</span><span class="o">-></span><span class="na">load</span><span class="o">-></span><span class="na">database</span><span class="p">(</span><span class="s1">'group_name'</span><span class="p">);</span>
</pre></div>
</div>
<p>Where group_name is the name of the connection group from your config
file.</p>
<p>To connect manually to a desired database you can pass an array of
values:</p>
<div class="highlight-ci"><div class="highlight"><pre><span class="nv">$config</span><span class="p">[</span><span class="s1">'hostname'</span><span class="p">]</span> <span class="o">=</span> <span class="s1">'localhost'</span><span class="p">;</span>
<span class="nv">$config</span><span class="p">[</span><span class="s1">'username'</span><span class="p">]</span> <span class="o">=</span> <span class="s1">'myusername'</span><span class="p">;</span>
<span class="nv">$config</span><span class="p">[</span><span class="s1">'password'</span><span class="p">]</span> <span class="o">=</span> <span class="s1">'mypassword'</span><span class="p">;</span>
<span class="nv">$config</span><span class="p">[</span><span class="s1">'database'</span><span class="p">]</span> <span class="o">=</span> <span class="s1">'mydatabase'</span><span class="p">;</span>
<span class="nv">$config</span><span class="p">[</span><span class="s1">'dbdriver'</span><span class="p">]</span> <span class="o">=</span> <span class="s1">'mysqli'</span><span class="p">;</span>
<span class="nv">$config</span><span class="p">[</span><span class="s1">'dbprefix'</span><span class="p">]</span> <span class="o">=</span> <span class="s1">''</span><span class="p">;</span>
<span class="nv">$config</span><span class="p">[</span><span class="s1">'pconnect'</span><span class="p">]</span> <span class="o">=</span> <span class="k">FALSE</span><span class="p">;</span>
<span class="nv">$config</span><span class="p">[</span><span class="s1">'db_debug'</span><span class="p">]</span> <span class="o">=</span> <span class="k">TRUE</span><span class="p">;</span>
<span class="nv">$config</span><span class="p">[</span><span class="s1">'cache_on'</span><span class="p">]</span> <span class="o">=</span> <span class="k">FALSE</span><span class="p">;</span>
<span class="nv">$config</span><span class="p">[</span><span class="s1">'cachedir'</span><span class="p">]</span> <span class="o">=</span> <span class="s1">''</span><span class="p">;</span>
<span class="nv">$config</span><span class="p">[</span><span class="s1">'char_set'</span><span class="p">]</span> <span class="o">=</span> <span class="s1">'utf8'</span><span class="p">;</span>
<span class="nv">$config</span><span class="p">[</span><span class="s1">'dbcollat'</span><span class="p">]</span> <span class="o">=</span> <span class="s1">'utf8_general_ci'</span><span class="p">;</span>
<span class="nv">$this</span><span class="o">-></span><span class="na">load</span><span class="o">-></span><span class="na">database</span><span class="p">(</span><span class="nv">$config</span><span class="p">);</span>
</pre></div>
</div>
<p>For information on each of these values please see the <a class="reference internal" href="configuration.html"><em>configuration
page</em></a>.</p>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p>For the PDO driver, you should use the $config[‘dsn’] setting
instead of ‘hostname’ and ‘database’:</p>
<div class="last line-block">
<div class="line"><br /></div>
<div class="line">$config[‘dsn’] = ‘mysql:host=localhost;dbname=mydatabase’;</div>
</div>
</div>
<p>Or you can submit your database values as a Data Source Name. DSNs must
have this prototype:</p>
<div class="highlight-ci"><div class="highlight"><pre><span class="nv">$dsn</span> <span class="o">=</span> <span class="s1">'dbdriver://username:password@hostname/database'</span><span class="p">;</span>
<span class="nv">$this</span><span class="o">-></span><span class="na">load</span><span class="o">-></span><span class="na">database</span><span class="p">(</span><span class="nv">$dsn</span><span class="p">);</span>
</pre></div>
</div>
<p>To override default config values when connecting with a DSN string, add
the config variables as a query string.</p>
<div class="highlight-ci"><div class="highlight"><pre><span class="nv">$dsn</span> <span class="o">=</span> <span class="s1">'dbdriver://username:password@hostname/database?char_set=utf8&dbcollat=utf8_general_ci&cache_on=true&cachedir=/path/to/cache'</span><span class="p">;</span>
<span class="nv">$this</span><span class="o">-></span><span class="na">load</span><span class="o">-></span><span class="na">database</span><span class="p">(</span><span class="nv">$dsn</span><span class="p">);</span>
</pre></div>
</div>
</div>
</div>
<div class="section" id="connecting-to-multiple-databases">
<h2>Connecting to Multiple Databases<a class="headerlink" href="#connecting-to-multiple-databases" title="Permalink to this headline">¶</a></h2>
<p>If you need to connect to more than one database simultaneously you can
do so as follows:</p>
<div class="highlight-ci"><div class="highlight"><pre><span class="nv">$DB1</span> <span class="o">=</span> <span class="nv">$this</span><span class="o">-></span><span class="na">load</span><span class="o">-></span><span class="na">database</span><span class="p">(</span><span class="s1">'group_one'</span><span class="p">,</span> <span class="k">TRUE</span><span class="p">);</span>
<span class="nv">$DB2</span> <span class="o">=</span> <span class="nv">$this</span><span class="o">-></span><span class="na">load</span><span class="o">-></span><span class="na">database</span><span class="p">(</span><span class="s1">'group_two'</span><span class="p">,</span> <span class="k">TRUE</span><span class="p">);</span>
</pre></div>
</div>
<p>Note: Change the words “group_one” and “group_two” to the specific
group names you are connecting to (or you can pass the connection values
as indicated above).</p>
<p>By setting the second parameter to TRUE (boolean) the function will
return the database object.</p>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p>When you connect this way, you will use your object name to issue
commands rather than the syntax used throughout this guide. In other
words, rather than issuing commands with:</p>
<div class="last line-block">
<div class="line"><br /></div>
<div class="line">$this->db->query();</div>
<div class="line">$this->db->result();</div>
<div class="line">etc...</div>
<div class="line"><br /></div>
<div class="line">You will instead use:</div>
<div class="line"><br /></div>
<div class="line">$DB1->query();</div>
<div class="line">$DB1->result();</div>
<div class="line">etc...</div>
</div>
</div>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p>You don’t need to create separate database configurations if you
only need to use a different database on the same connection. You
can switch to a different database when you need to, like this:</p>
<div class="last line-block">
<div class="line">$this->db->db_select($database2_name);</div>
</div>
</div>
</div>
<div class="section" id="reconnecting-keeping-the-connection-alive">
<h2>Reconnecting / Keeping the Connection Alive<a class="headerlink" href="#reconnecting-keeping-the-connection-alive" title="Permalink to this headline">¶</a></h2>
<p>If the database server’s idle timeout is exceeded while you’re doing
some heavy PHP lifting (processing an image, for instance), you should
consider pinging the server by using the reconnect() method before
sending further queries, which can gracefully keep the connection alive
or re-establish it.</p>
<div class="highlight-ci"><div class="highlight"><pre><span class="nv">$this</span><span class="o">-></span><span class="na">db</span><span class="o">-></span><span class="na">reconnect</span><span class="p">();</span>
</pre></div>
</div>
</div>
<div class="section" id="manually-closing-the-connection">
<h2>Manually closing the Connection<a class="headerlink" href="#manually-closing-the-connection" title="Permalink to this headline">¶</a></h2>
<p>While CodeIgniter intelligently takes care of closing your database
connections, you can explicitly close the connection.</p>
<div class="highlight-ci"><div class="highlight"><pre><span class="nv">$this</span><span class="o">-></span><span class="na">db</span><span class="o">-></span><span class="na">close</span><span class="p">();</span>
</pre></div>
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