PDO::prepare

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Prepares a statement for execution.

Syntax

PDOStatement PDO::prepare ( $statement [, array(key_pair)] )

Parameters

$statement: A string containing the SQL statement.

key_pair: An array containing an attribute name and value. See the Remarks section for more information.

Return Value

Returns a PDOStatement object on success. On failure, returns a PDOException object, or false depending on the value of PDO::ATTR_ERRMODE.

Remarks

The Microsoft Drivers for PHP for SQL Server does not evaluate prepared statements until execution.

The following table lists the possible key_pair values.

When using PDO::ATTR_CURSOR => PDO::CURSOR_SCROLL, you can use PDO::SQLSRV_ATTR_CURSOR_SCROLL_TYPE to specify the type of cursor. For example, pass the following array to PDO::prepare to set a dynamic cursor:

array(PDO::ATTR_CURSOR => PDO::CURSOR_SCROLL, PDO::SQLSRV_ATTR_CURSOR_SCROLL_TYPE => PDO::SQLSRV_CURSOR_DYNAMIC));

The following table shows the possible values for PDO::SQLSRV_ATTR_CURSOR_SCROLL_TYPE. For more information about scrollable cursors, see Cursor Types (PDO_SQLSRV Driver).

You can close a PDOStatement object by calling unset:

unset($stmt);

Forward-only example

This example shows how to use PDO::prepare with parameter markers and a forward-only cursor.

<?php
$database = "Test";
$server = "(local)";
$conn = new PDO( "sqlsrv:server=$server ; Database = $database", "", "");

$col1 = 'a';
$col2 = 'b';

$query = "insert into Table1(col1, col2) values(?, ?)";
$stmt = $conn->prepare( $query, array( PDO::ATTR_CURSOR => PDO::CURSOR_FWDONLY, PDO::SQLSRV_ATTR_QUERY_TIMEOUT => 1  ) );
$stmt->execute( array( $col1, $col2 ) );
print $stmt->rowCount();
echo "\n";

$query = "insert into Table1(col1, col2) values(:col1, :col2)";
$stmt = $conn->prepare( $query, array( PDO::ATTR_CURSOR => PDO::CURSOR_FWDONLY, PDO::SQLSRV_ATTR_QUERY_TIMEOUT => 1  ) );
$stmt->execute( array( ':col1' => $col1, ':col2' => $col2 ) );
print $stmt->rowCount();

unset($stmt);
?>

Static cursor example

This example shows how to use PDO::prepare with a server-side static cursor. For an example showing a client-side cursor, see Cursor Types (PDO_SQLSRV Driver).

<?php
$database = "AdventureWorks";
$server = "(local)";
$conn = new PDO( "sqlsrv:server=$server ; Database = $database", "", "");

$query = "select * from Person.ContactType";
$stmt = $conn->prepare( $query, array(PDO::ATTR_CURSOR => PDO::CURSOR_SCROLL));
$stmt->execute();

echo "\n";

while ( $row = $stmt->fetch( PDO::FETCH_ASSOC ) ){
   print "$row[Name]\n";
}
echo "\n..\n";

$row = $stmt->fetch( PDO::FETCH_BOTH, PDO::FETCH_ORI_FIRST );
print_r($row);

$row = $stmt->fetch( PDO::FETCH_ASSOC, PDO::FETCH_ORI_REL, 1 );
print "$row[Name]\n";

$row = $stmt->fetch( PDO::FETCH_NUM, PDO::FETCH_ORI_NEXT );
print "$row[1]\n";

$row = $stmt->fetch( PDO::FETCH_NUM, PDO::FETCH_ORI_PRIOR );
print "$row[1]..\n";

$row = $stmt->fetch( PDO::FETCH_NUM, PDO::FETCH_ORI_ABS, 0 );
print_r($row);

$row = $stmt->fetch( PDO::FETCH_NUM, PDO::FETCH_ORI_LAST );
print_r($row);
?>

Targeted example

The following two snippets show how to use PDO::prepare with data targeted for CHAR/VARCHAR columns. Because the default encoding for PDO::prepare is UTF-8, the user can use the option PDO::SQLSRV_ENCODING_SYSTEM to avoid implicit conversions.

Option 1

$options = array(PDO::SQLSRV_ATTR_ENCODING => PDO::SQLSRV_ENCODING_SYSTEM);
$statement = $pdo->prepare(
  'SELECT *
   FROM myTable
   WHERE myVarcharColumn = :myVarcharValue',
  $options
);

$statement->bindValue(':myVarcharValue', 'my data', PDO::PARAM_STR);

Option 2

$statement = $pdo->prepare(
  'SELECT *
   FROM myTable
   WHERE myVarcharColumn = :myVarcharValue'
);
$p = 'my data';
$statement->bindParam(':myVarcharValue', $p, PDO::PARAM_STR, 0, PDO::SQLSRV_ENCODING_SYSTEM);

Prepare example

This example shows how to use PDO::prepare with PDO::ATTR_EMULATE_PREPARES set to true.

<?php
$serverName = "yourservername";
$username = "yourusername";
$password = "yourpassword";
$database = "tempdb";
$conn = new PDO("sqlsrv:server = $serverName; Database = $database", $username, $password);

$pdo_options = array();
$pdo_options[PDO::ATTR_EMULATE_PREPARES] = true;
$pdo_options[PDO::SQLSRV_ATTR_ENCODING] = PDO::SQLSRV_ENCODING_UTF8;

$stmt = $conn->prepare("CREATE TABLE TEST([id] [int] IDENTITY(1,1) NOT NULL,
                                          [name] nvarchar(max))",
                                          $pdo_options);
$stmt->execute();

$prefix = '가각';
$name = '가각ácasa';
$name2 = '가각sample2';

$stmt = $conn->prepare("INSERT INTO TEST(name) VALUES(:p0)", $pdo_options);
$stmt->execute(['p0' => $name]);
unset($stmt);

$stmt = $conn->prepare("SELECT * FROM TEST WHERE NAME LIKE :p0", $pdo_options);
$stmt->execute(['p0' => "$prefix%"]);
foreach ($stmt as $row) {
    echo "\n" . 'FOUND: ' . $row['name'];
}

unset($stmt);
unset($conn);
?>

The PDO_SQLSRV driver internally replaces all the placeholders with the parameters that are bound by PDOStatement::bindParam(). Therefore, a SQL query string with no placeholders is sent to the server. Consider this example,

$statement = $PDO->prepare("INSERT into Customers (CustomerName, ContactName) VALUES (:cus_name, :con_name)");
$statement->bindParam(:cus_name, "Cardinal");
$statement->bindParam(:con_name, "Tom B. Erichsen");
$statement->execute();

With PDO::ATTR_EMULATE_PREPARES set to false (the default case), the data sent to the database is:

"INSERT into Customers (CustomerName, ContactName) VALUES (:cus_name, :con_name)"
Information on :cus_name parameter
Information on :con_name parameter

The server will execute the query using its parameterized query feature for binding parameters. On the other hand, with PDO::ATTR_EMULATE_PREPARES set to true, the query sent to the server is essentially:

"INSERT into Customers (CustomerName, ContactName) VALUES ('Cardinal', 'Tom B. Erichsen')"

Setting PDO::ATTR_EMULATE_PREPARES to true can bypass some restrictions in SQL Server. For example, SQL Server does not support named or positional parameters in some Transact-SQL clauses. Moreover, SQL Server has a limit of binding 2100 parameters.

Encoding

If user wishes to bind parameters with different encodings (for instance, UTF-8 or binary), user should clearly specify the encoding in the PHP script.

The PDO_SQLSRV driver first checks the encoding specified in PDO::bindParam() (for example, $statement->bindParam(:cus_name, "Cardinal", PDO::PARAM_STR, 10, PDO::SQLSRV_ENCODING_UTF8)).

If not found, the driver checks if any encoding is set in PDO::prepare() or PDOStatement::setAttribute(). Otherwise, the driver will use the encoding specified in PDO::__construct() or PDO::setAttribute().

In addition, beginning with version 5.8.0, when using PDO::prepare with PDO::ATTR_EMULATE_PREPARES set to true, the user may use the extended string types introduced in PHP 7.2 to ensure that the N prefix is used. The snippets below display various alternatives.

Using driver option PDO::SQLSRV_ENCODING_UTF8 when binding

$p = '가각';
$sql = 'SELECT :value';
$options = array(PDO::ATTR_EMULATE_PREPARES => true);
$stmt = $conn->prepare($sql, $options);
$stmt->bindParam(':value', $p, PDO::PARAM_STR, 0, PDO::SQLSRV_ENCODING_UTF8);
$stmt->execute();

Using the PDO::SQLSRV_ATTR_ENCODING attribute

$p = '가각';
$sql = 'SELECT :value';
$options = array(PDO::ATTR_EMULATE_PREPARES => true, PDO::SQLSRV_ATTR_ENCODING => PDO::SQLSRV_ENCODING_UTF8);
$stmt = $conn->prepare($sql, $options);
$stmt->execute([':value' => $p]);

Using the PDO constant PDO::PARAM_STR_NATL

$p = '가각';
$sql = 'SELECT :value';
$options = array(PDO::ATTR_EMULATE_PREPARES => true);
$stmt = $conn->prepare($sql, $options);
$stmt->bindParam(':value', $p, PDO::PARAM_STR | PDO::PARAM_STR_NATL);
$stmt->execute();

Setting the default string param type PDO::PARAM_STR_NATL

$conn->setAttribute(PDO::ATTR_DEFAULT_STR_PARAM, PDO::PARAM_STR_NATL);
$p = '가각';
$sql = 'SELECT :value';
$options = array(PDO::ATTR_EMULATE_PREPARES => true);
$stmt = $conn->prepare($sql, $options);
$stmt->execute([':value' => $p]);

Limitations

As you can see, binding is done internally by the driver. A valid query is sent to the server for execution without any parameter. Compared to the regular case, some limitations result when the parameterized query feature is not in use.

• It does not work for parameters that are bound as PDO::PARAM_INPUT_OUTPUT.
  • When the user specifies PDO::PARAM_INPUT_OUTPUT in PDO::bindParam(), a PDO exception is thrown.
• It does not work for parameters that are bound as output parameters.
  • When the user creates a prepared statement with placeholders that are meant for output parameters (that is, having an equal sign immediately after a placeholder, like SELECT ? = COUNT(*) FROM Table1), a PDO exception is thrown.
  • When a prepared statement invokes a stored procedure with a placeholder as the argument for an output parameter, no exception is thrown because the driver cannot detect the output parameter. However, the variable that the user provides for the output parameter will remain unchanged.
• Duplicated placeholders for a binary encoded parameter will not work

See Also

PDO Class

PDO