How to Retrieve Output from MySQL Stored Procedures Using PDO in PHP?

Retrieving MySQL Stored Procedure Variables in PHP Using PDO

Problem:

How can I retrieve the LAST_INSERT_ID() value from a MySQL stored procedure using PHP and PDO?

Procedure:

Consider the following PHP code:

<?php
$stmt = $db->prepare("CALL simpleProcedure(:name,:returnid)");
$stmt->bindValue(':name', $name, PDO::PARAM_STR);
$stmt->bindParam(':returnid', $returnid, PDO::PARAM_INT, 11);
$stmt->execute();
echo $returnid;
?>

While this code may seem correct, it does not work due to a long-standing bug in PDO.

Solution:

To retrieve the output from a MySQL procedure, follow these steps:

Step 1: Run the Procedure

Run the procedure with your inputs and specify which MySQL variables will store the results. For example:

<?php
$stmt = $db->prepare("CALL simpleProcedure(:name, @returnid)");
$stmt->bindValue(':name', $name, PDO::PARAM_STR);
$stmt->execute();
?>

Step 2: Query the MySQL Variables

Run a separate query to select the MySQL variables:

<?php
$stmt = $db->query("SELECT @returnid");
$result = $stmt->fetchAll(PDO::FETCH_COLUMN, 0);
$returnid = $result[0];
?>

Example:

The following code includes a more detailed example showing the use of variables for different parameter types (IN, INOUT, OUT):

SQL Procedure:

CREATE PROCEDURE `demoSpInOutSqlVars`(
    IN     pInput_Param  INT, 
    /* --- */  
    INOUT  pInOut_Param  INT, 
    OUT    pOut_Param    INT)
BEGIN
    /*
     * Pass the full names of SQL User Variable for these parameters. e.g. '@varInOutParam'
     * These 'SQL user variables names' are the variables that Mysql will use for:
     *    1) finding values
     *    2) storing results
     *
     * It is similar to 'variable variables' in PHP.  
     */
     SET pInOut_Param      := ABS(pInput_Param) + ABS(pInOut_Param); 
     SET pOut_Param        := ABS(pInput_Param) * -3;                
END$$

PHP Code:

<?php
// Bind PHP variables
$phpInParam = 5;                  
$phpInOutParam = 404;
$phpOutParam = null;

// Prepare the SQL procedure call
$sql = "call demoSpInOut(:phpInParam, 
                         @varInOutParam, 
                         @varOutParam)";

$stmt = $db->prepare($sql);
$stmt->bindParam(':phpInParam', $phpInParam, PDO::PARAM_INT);

// Set the SQL User INOUT variables
$db->exec("SET @varInOutParam = $phpInOutParam");

// Execute the procedure
$stmt->execute();

// Get the SQL variables into PHP variables
$sql = "SELECT @varInOutParam AS phpInOutParam,
               @varOutParam   AS phpOutParam
        FROM dual";

$results = $db->query($sql)->fetchAll(PDO::FETCH_ASSOC);
$phpInOutParam = $results[0]['phpInOutParam'];
$phpOutParam = $results[0]['phpOutParam'];

// Display the PHP variables
echo "phpInParam: $phpInParam<br>";
echo "phpInOutParam: $phpInOutParam<br>";
echo "phpOutParam: $phpOutParam<br>";
?>

By following these steps, you can effectively retrieve the output from MySQL stored procedures using PDO.

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