- Recall that:
$result = mysqli_query($conn, $query) $result = the result set returned by the execution of the query
- The $result result set
contains:
- The data
(= the tuples in the
result)
- The meta data about the tuples (= data) in the result set !!!
- The data
(= the tuples in the
result)
- The PHP function
mysqli_fetch_field($result):
$metaDataObj = mysqli_fetch_field($result) ; // Get meta data of the next column/field mysqli_fetch_field($result) returns: a meta data object "stdClass" object that contains the meta data of the next column (attribute) in the result set $result
- How to
use
the
mysqli_fetch_field($result)
function to
retrieve
the meta data information
of all attributes:
$result = mysqli_query($conn, $query); // Execute a query /* ============================================================== Print (ALL) the meta data of each attribute in the result set NOTE: mysqli_fetch_field($result) returns an OBJECT =============================================================== */ while ( ($x = mysqli_fetch_field($result)) != NULL ) { /* ------------------------------------------------ $x contains the meta data of the next attribute ------------------------------------------------ */ print_r($x); // Print the meta data of one attr }
- Structure of the
meta data:
- The meta data of a result set contains different information on each field (attribute) in the result set
Example 1:
- The meta data of
the result set of
the following query:
select fname from employee
consists of the following stdClass object:
stdClass Object ( [name] => fname [orgname] => fname [table] => employee [orgtable] => employee [def] => [db] => companyDB [catalog] => def [max_length] => 6 [length] => 6 [charsetnr] => 8 [flags] => 4097 [type] => 254 [decimals] => 0 )
Example 2:
- The meta data of
the result set of
the following query:
select fname FN, lname LN from employee
consists of the following 2 stdClass objects:
stdClass Object ( [name] => FN [orgname] => fname [table] => employee [orgtable] => employee [def] => [db] => companyDB [catalog] => def [max_length] => 6 [length] => 6 [charsetnr] => 8 [flags] => 4097 [type] => 254 [decimals] => 0 ) stdClass Object ( [name] => LN [orgname] => lname [table] => employee [orgtable] => employee [def] => [db] => companyDB [catalog] => def [max_length] => 7 [length] => 8 [charsetnr] => 8 [flags] => 4097 [type] => 254 [decimals] => 0 )
- Note:
if you only want to
get the
attribute name, then use:
$result = mysqli_query($conn, $query); // Execute a query /* ============================================================== Print ALL the meta data of each attribute in the result set NOTE: mysqli_fetch_field($result) returns an OBJECT =============================================================== */ while ( ($x = mysqli_fetch_field($result)) != NULL ) { print($x->name); }
- Example Program:
(Demo above code)
ssh -X holland Run: /home/cs377001/PHP/intro-PHP/employee-metadata.php