How to: Handle Errors and Warnings Using the SQLSRV Driver

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By default, the SQLSRV driver treats warnings as errors; a call to a sqlsrv function that generates an error or a warning returns false. This topic demonstrates how to turn off this default behavior and how to handle warnings separately from errors.

Example

The following code example uses two user-defined functions, DisplayErrors and DisplayWarnings, to handle errors and warnings. The example demonstrates how to handle warnings and errors separately by doing the following:

1. Turns off the default behavior of treating warnings as errors.

2. Creates a stored procedure that updates an employee's vacation hours and returns the remaining vacation hours as an output parameter. When an employee's available vacation hours are less than zero, the stored procedure prints a warning.

3. Updates vacation hours for several employees by calling the stored procedure for each employee, and displays the messages that correspond to any warnings and errors that occur.

4. Displays the remaining vacation hours for each employee.

In the first call to a sqlsrv function (sqlsrv_configure), warnings are treated as errors. Because warnings are added to the error collection, you do not have to check for warnings separately from errors. In subsequent calls to sqlsrv functions, however, warnings will not be treated as errors, so you must check explicitly for warnings and for errors.

Also note that the example code checks for errors after each call to a sqlsrv function. This is the recommended practice.

This example assumes that SQL Server and the AdventureWorks database are installed on the local computer. All output is written to the console when the example is run from the command line. When the example is run against a new installation of the AdventureWorks database, it produces three warnings and two errors. The first two warnings are standard warnings that are issued when you connect to a database. The third warning occurs because an employee's available vacation hours are updated to a value less than zero. The errors occur because an employee's available vacation hours are updated to a value less than -40 hours, which is a violation of a constraint on the table.

<?php  
/* Turn off the default behavior of treating errors as warnings.  
Note: Turning off the default behavior is done here for demonstration  
purposes only. If setting the configuration fails, display errors and  
exit the script. */  
if( sqlsrv_configure("WarningsReturnAsErrors", 0) === false)  
{  
     DisplayErrors();  
     die;  
}  
  
/* Connect to the local server using Windows Authentication and   
specify the AdventureWorks database as the database in use. */  
$serverName = "(local)";  
$connectionInfo = array("Database"=>"AdventureWorks");  
$conn = sqlsrv_connect( $serverName, $connectionInfo);  
  
/* If the connection fails, display errors and exit the script. */  
if( $conn === false )  
{  
     DisplayErrors();  
     die;  
}  
/* Display any warnings. */  
DisplayWarnings();  
  
/* Drop the stored procedure if it already exists. */  
$tsql1 = "IF OBJECT_ID('SubtractVacationHours', 'P') IS NOT NULL  
                DROP PROCEDURE SubtractVacationHours";  
$stmt1 = sqlsrv_query($conn, $tsql1);  
  
/* If the query fails, display errors and exit the script. */  
if( $stmt1 === false)  
{  
     DisplayErrors();  
     die;  
}  
/* Display any warnings. */  
DisplayWarnings();  
  
/* Free the statement resources. */  
sqlsrv_free_stmt( $stmt1 );  
  
/* Create the stored procedure. */  
$tsql2 = "CREATE PROCEDURE SubtractVacationHours  
                  @EmployeeID int,  
                  @VacationHours smallint OUTPUT  
              AS  
                  UPDATE HumanResources.Employee  
                  SET VacationHours = VacationHours - @VacationHours  
                  WHERE EmployeeID = @EmployeeID;  
                  SET @VacationHours = (SELECT VacationHours    
                                       FROM HumanResources.Employee  
                                       WHERE EmployeeID = @EmployeeID);  
              IF @VacationHours < 0   
              BEGIN  
                PRINT 'WARNING: Vacation hours are now less than zero.'  
              END;";  
$stmt2 = sqlsrv_query( $conn, $tsql2 );  
  
/* If the query fails, display errors and exit the script. */  
if( $stmt2 === false)  
{  
     DisplayErrors();  
     die;  
}  
/* Display any warnings. */  
DisplayWarnings();  
  
/* Free the statement resources. */  
sqlsrv_free_stmt( $stmt2 );  
  
/* Set up the array that maps employee ID to used vacation hours. */  
$emp_hrs = array (7=>4, 8=>5, 9=>8, 11=>50);  
  
/* Initialize variables that will be used as parameters. */  
$employeeId = 0;  
$vacationHrs = 0;  
  
/* Set up the parameter array. */  
$params = array(  
                 array(&$employeeId, SQLSRV_PARAM_IN),  
                 array(&$vacationHrs, SQLSRV_PARAM_INOUT)  
                );  
  
/* Define and prepare the query to subtract used vacation hours. */  
$tsql3 = "{call SubtractVacationHours(?, ?)}";  
$stmt3 = sqlsrv_prepare($conn, $tsql3, $params);  
  
/* If the statement preparation fails, display errors and exit the script. */  
if( $stmt3 === false)  
{  
     DisplayErrors();  
     die;  
}  
/* Display any warnings. */  
DisplayWarnings();  
  
/* Loop through the employee=>vacation hours array. Update parameter  
 values before statement execution. */  
foreach(array_keys($emp_hrs) as $employeeId)  
{  
     $vacationHrs = $emp_hrs[$employeeId];  
     /* Execute the query.  If it fails, display the errors. */  
     if( sqlsrv_execute($stmt3) === false)  
     {  
          DisplayErrors();  
          die;  
     }  
     /* Display any warnings. */  
     DisplayWarnings();  
  
     /*Move to the next result returned by the stored procedure. */  
     if( sqlsrv_next_result($stmt3) === false)  
     {  
          DisplayErrors();  
          die;  
     }  
     /* Display any warnings. */  
     DisplayWarnings();  
  
     /* Display updated vacation hours. */  
     echo "EmployeeID $employeeId has $vacationHrs ";  
     echo "remaining vacation hours.\n";  
}  
  
/* Free the statement and connection resources. */  
sqlsrv_free_stmt( $stmt3 );  
sqlsrv_close( $conn );  
  
/* ------------- Error Handling Functions --------------*/  
function DisplayErrors()  
{  
     $errors = sqlsrv_errors(SQLSRV_ERR_ERRORS);  
     foreach( $errors as $error )  
     {  
          echo "Error: ".$error['message']."\n";  
     }  
}  
  
function DisplayWarnings()  
{  
     $warnings = sqlsrv_errors(SQLSRV_ERR_WARNINGS);  
     if(!is_null($warnings))  
     {  
          foreach( $warnings as $warning )  
          {  
               echo "Warning: ".$warning['message']."\n";  
          }  
     }  
}  
?>  

See Also

How to: Configure Error and Warning Handling Using the SQLSRV Driver

SQLSRV Driver API Reference