Last updated: Fri, 03 Jul 2009

mysql_fetch_field

(PHP 4, PHP 5)

mysql_fetch_field — Get column information from a result and return as an object

Description

object mysql_fetch_field ( resource $result [, int $field_offset= 0 ] )

Returns an object containing field information. This function can be used to obtain information about fields in the provided query result.

Parameters

result: The result resource that is being evaluated. This result comes from a call to mysql_query().
field_offset: The numerical field offset. If the field offset is not specified, the next field that was not yet retrieved by this function is retrieved. The field_offset starts at 0.

Return Values

Returns an object containing field information. The properties of the object are:

name - column name
table - name of the table the column belongs to
def - default value of the column
max_length - maximum length of the column
not_null - 1 if the column cannot be NULL
primary_key - 1 if the column is a primary key
unique_key - 1 if the column is a unique key
multiple_key - 1 if the column is a non-unique key
numeric - 1 if the column is numeric
blob - 1 if the column is a BLOB
type - the type of the column
unsigned - 1 if the column is unsigned
zerofill - 1 if the column is zero-filled

Examples

Example #1 mysql_fetch_field() example


<?php
$conn = mysql_connect('localhost', 'mysql_user', 'mysql_password');
if (!$conn) {
    die('Could not connect: ' . mysql_error());
}
mysql_select_db('database');
$result = mysql_query('select * from table');
if (!$result) {
    die('Query failed: ' . mysql_error());
}
/* get column metadata */
$i = 0;
while ($i < mysql_num_fields($result)) {
    echo "Information for column $i:<br />\n";
    $meta = mysql_fetch_field($result, $i);
    if (!$meta) {
        echo "No information available<br />\n";
    }
    echo "<pre>
blob:         $meta->blob
max_length:   $meta->max_length
multiple_key: $meta->multiple_key
name:         $meta->name
not_null:     $meta->not_null
numeric:      $meta->numeric
primary_key:  $meta->primary_key
table:        $meta->table
type:         $meta->type
default:      $meta->def
unique_key:   $meta->unique_key
unsigned:     $meta->unsigned
zerofill:     $meta->zerofill
</pre>";
    $i++;
}
mysql_free_result($result);
?>

Notes

Note: Field names returned by this function are case-sensitive.


XML generation.



Bit of a security risk allowing parameters to select db and table on live server (unless user is restricted or replace the $_GET with fixed value.)



Outputs xml with standard format for <config> part to generate forms in flash.



<?php

    //

    //    makeXML.php?db=dbname&table=tablename

    //

    

    set_time_limit(300);

        

    $host = "localhost";

    $user = "root";

    $password = "root";

    

    $database = $_GET['db'];    

    $table = $_GET['table'];

    

    mysql_connect($host,$user,$password);

    @mysql_select_db($database) or die( "Unable to select database");

    



    $querytext="SELECT * FROM ".$table;  

    $result=mysql_query($querytext);

    

    if ($result){

        $num=mysql_num_rows($result);

    }else{

        $num=0;

    }

    

?>

<?php 

    header('Content-Type: text/xml');

     echo "<?xml version='1.0'?>"; 

     

     if ($num > 0){

 ?>

<<?php  echo $table?>>

    <config>

        <?php

            // Display number of fields

            echo "<numFields>".mysql_num_fields($result)."</numFields>";

            $i = 0;

            $primaryKey = "";

            $nameArray = array(); 

            $maxLengthArray = array(); 

            $typeArray = array(); 

            while ($i < mysql_num_fields($result)) {

                $meta = mysql_fetch_field($result, $i);

                $nameArray[$i] = $meta->name;

                $maxLengthArray[$i] = $meta->max_length;

                $typeArray[$i] = $meta->type;

                if ($meta->primary_key){

                    $primaryKey = $meta->name;

                }

                $i++;

            }

            $i = 0;

            echo "<fieldNames>";

            while ($i < count($nameArray)) {

                echo "<field".$i.">".$nameArray[$i]."</field".$i.">";

                $i++;

            }

            echo "</fieldNames>";

            $i = 0;

            echo "<fieldMaxLength>";

            while ($i < count($maxLengthArray)) {

                echo "<field".$i.">".$maxLengthArray[$i]."</field".$i.">";

                $i++;

            }

            echo "</fieldMaxLength>";

            $i = 0;

            echo "<fieldType>";

            while ($i < count($typeArray)) {

                echo "<field".$i.">".$typeArray[$i]."</field".$i.">";

                $i++;

            }

            echo "</fieldType>";

        ?>

        <primaryKey><?php  echo $primaryKey?></primaryKey>

        <numRecords><?php  echo $num?></numRecords>

    </config>

<?php  

    $i=0;

    while ($i < $num) {

        $ID=mysql_result($result,$i,"ID");

        $value=mysql_result($result,$i,"value");

        $title=mysql_result($result,$i,"title");

        $description=mysql_result($result,$i,"description");

?>

    <row>

        <ID><?php  echo $ID?></ID>

        <weighting><?php  echo $value?></weighting>

        <title><?php  echo $title?></title>

        <description><?php  echo $description?></description>

    </row>

<?php 

        $i = $i + 1;

    } 

?>

</<?php  echo $table?>>



<?php 

    } 

?>

php [spat] hm2k.org
05-Nov-2008 01:22


An improvement on the earlier mysql_column_exists function.



<?php



function mysql_column_exists($table_name, $column_name, $link=false) {

    $result = @mysql_query("SHOW COLUMNS FROM $table_name LIKE '$column_name'", $link);

    return (mysql_num_rows($result) > 0);

}



?>

jorachim at geemail dot com
25-Sep-2008 11:09


If you want the fields in a table, a simple DESCRIBE query will work:



<?php

$query ="DESCRIBE Users";

$result = mysql_query($query);



echo "<ul>";



while($i = mysql_fetch_assoc($result))

     echo "<li>{$i['Field']}</li>";



echo "</ul>";

?>



Should do the trick.

david at vitam dot be
10-Jun-2008 03:57


A little function to help coders to distinct the tablename from a multiselect query where some fields has the same name in differents tables.





<?php


public function sql($sql) {


    $T_Return=array();


    $result=@mysql_query($sql);


    


    $i=0;


    while ($i < mysql_num_fields($result)) {            


        $fields[]=mysql_fetch_field($result, $i);


        $i++;


    }


    


    while ($row=mysql_fetch_row($result)) {                


        $new_row=array();


        for($i=0;$i<count($row); $i++) {


            $new_row[ $fields[$i]->table][$fields[$i]->name]=$row[$i];


        }


        $T_Return[]=$new_row;


    }





    


    return $T_Return;


}


?>

dheep
04-Jun-2008 06:56


Simple PHP script for displaying the field names. Presuming the database is seleected already.





<?php


$sql = "SELECT * FROM table_name;";


$result = mysql_query($sql);


$i = 0;


while($i<mysql_num_fields($result))


{


  $meta=mysql_fetch_field($result,$i);


  echo $i.".".$meta->name."<br />";


  $i++;


}


?>





OUTPUt:


0.id


1.todo


2.due date


3.priority


4.type


5.status


6.notes





hope this is useful.

Nick Baicoianu
15-Sep-2005 09:18


Be sure to note that $max_length is the length of the longest value for that field in the returned dataset, NOT the maximum length of data that column is designed to hold.

php at brayra dot com
22-Mar-2002 02:09


I needed to get the field information and the enum/set values. Here is the function I created to expand the object returned by mysql_fetch_field. I also, decided to return all the fields for a table in an array of field objects by "name" and position much like mysql_fetch_array does.





You could test it by using:





<?php


$myfields = GetFieldInfo('test_table');


print "<pre>";


print_r($myfields);


print "</pre>";


?>








The field objects now have 'len', 'values' and 'flags' parameters. 


NOTE: 'values' only has data for set and enum fields.





<?php


//This assumes an open database connection


//I also use a constant DB_DB for current database.


function GetFieldInfo($table)


{


  if($table == '') return false;


  $fields = mysql_list_fields(DB_DB, $table);


  if($fields){


    $columns = mysql_query('show columns from ' . $table);


    if($columns){


      $num = mysql_num_fields($fields);


      for($i=0; $i < $num; ++$i){


        $column = mysql_fetch_array($columns);


        $field = mysql_fetch_field($fields, $i);


        $flags = mysql_field_flags($fields, $i);


        if($flags == '') $flags=array();


        else $flags = explode(' ',$flags);


        if (ereg('enum.(.*).',$column['Type'],$match))


          $field->values = explode(',',$match[1]);


        if (ereg('set.(.*).',$column['Type'],$match))


          $field->values = explode(',',$match[1]);


        if(!$field->values) $field->values = array();


        $field->flags = $flags;


        $field->len = mysql_field_len($fields, $i);


        $result_fields[$field->name] = $field;


        $result_fields[$i] = $field;


      }


      mysql_free_result($columns);


    }


    mysql_free_result($fields);


    return $result_fields;


  }


  return false;


}


?>





hope someone else finds this useful.

krang at krang dot org dot uk
10-Mar-2002 04:12


The field type returns what PHP classifies the data found in the field, not how it is stored in the database; use the following example to retrieve the MySQL information about the field....





<?php


$USERNAME = '';


$PASSWORD = '';





$DATABASE = '';


$TABLE_NAME = '';





mysql_connect('localhost', $USERNAME, $PASSWORD)


    or die ("Could not connect");





$result = mysql_query("SHOW FIELDS FROM $DATABASE.$TABLE_NAME");





$i = 0;





while ($row = mysql_fetch_array($result)) {


  echo $row['Field'] . ' ' . $row['Type'];


}


?>

add a note

mysql_fetch_lengths

mysql_fetch_assoc