mysql_fetch_field

(PHP 4, PHP 5)

mysql_fetch_field — Liefert ein Objekt mit Spalteninformationen aus einem Abfrageergebnis

Warnung

Diese Erweiterung ist seit PHP 5.5.0 als veraltet markiert und wurde in PHP 7.0.0 entfernt. Verwenden Sie stattdessen die Erweiterungen MySQLi oder PDO_MySQL. Weitere Informationen bietet der Ratgeber MySQL: Auswahl einer API. Alternativen zu dieser Funktion umfassen:

Beschreibung

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

Gibt ein Objekt zurück, das Feldinformationen enthält. Diese Funktion kann verwendet werden, um Informationen über Felder im übergebenen Abfrageergebnis zu erhalten.

Parameter-Liste

result: Das Ergebnis Ressource, das ausgewertet wird. Dieses Ergebnis kommt von einem Aufruf von mysql_query().
field_offset: Der numerische Feldoffset. Wird dieser nicht angegeben, so werden die Informationen über das nächste bisher noch nicht von dieser Funktion gelesene Feld zurückgegeben. Der Feldoffset startet bei 0.

Rückgabewerte

Gibt ein Objekt mit Feldinformationen zurück. Die Eigenschaften des Objekts sind:

name - Spaltenname
table - der Name der Tabelle, zu der die Spalte gehört, wobei dies der Aliasname ist falls, einer definiert wurde
max_length - die maximale Länge der Spalte
not_null - 1, wenn die Spalte nicht null sein kann
primary_key - 1, wenn die Spalte ein Primärschlüssel ist
unique_key - 1, wenn die Spalte ein eindeutiger Schlüssel ist
multiple_key - 1, wenn die Spalte ein nicht eindeutiger Schlüssel ist
numeric - 1, wenn die Spalte vom Typ 'numeric' ist
blob - 1, wenn die Saplte vom Typ 'BLOB' ist
type - der Typ der Spalte
unsigned - 1, wenn die Spalte vorzeichenlos ist
zerofill - 1, wenn die Spalte mit Nullen aufgefüllt wird (zero-filled)

Beispiele

Beispiel #1 mysql_fetch_field()-Beispiel

<?php
$conn = mysql_connect('localhost', 'mysql_user', 'mysql_password');
if (!$conn) {
    die('Keine Verbindung möglich: ' . mysql_error());
}
mysql_select_db('database');
$result = mysql_query('select * from table');
if (!$result) {
    die('Anfrage fehlgeschlagen: ' . mysql_error());
}
/* Metadaten der Spalten holen */
$i = 0;
while ($i < mysql_num_fields($result)) {
    echo "Informationen für Spalte $i:<br />\n";
    $meta = mysql_fetch_field($result, $i);
    if (!$meta) {
        echo "Keine Informationen vorhanden<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
unique_key:   $meta->unique_key
unsigned:     $meta->unsigned
zerofill:     $meta->zerofill
</pre>";
    $i++;
}
mysql_free_result($result);
?>

Anmerkungen

Hinweis: Bei den Spaltennamen, die von dieser Funktion zurückgegeben werden, wird zwischen Groß- und Kleinschreibung unterschieden.

Hinweis:
Falls Feld- oder Tabellennamen in der SQL-Abfrage mit einem Alias versehen wurden, so wird dieser zurückgegeben. Der ursprüngliche Name kann beispielsweise durch die Verwendung von mysqli_result::fetch_field() in Erfahrung gebracht werden.

Siehe auch

mysql_field_seek() - Setzt den Ergebniszeiger auf einen bestimmten Feldoffset

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User Contributed Notes 12 notes

down

david at vitam dot be ¶

16 years ago

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;

}

?>

down

krang at krang dot org dot uk ¶

22 years ago

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'];

}

?>

down

Nick Baicoianu ¶

19 years ago

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.

down

-1

lucien at ocia dot nl ¶

12 years ago

Performance Notes!

I used this script for testing, the table has 26 colums.

<?php
$t_start = microtime(true);
$sql = mysql_query("SELECT * FROM `table` LIMIT 1") or trigger_error(mysql_error(), E_USER_WARNING);
for ($i = 0; $i < mysql_num_fields($sql); $i++) {
    $meta = mysql_fetch_field($sql, $i);
    echo "Information for column ".$meta->name.":\n";
    echo 
"\tblob:         $meta->blob
\tmax_length:   $meta->max_length
\tmultiple_key: $meta->multiple_key
\tname:         $meta->name
\tnot_null:     $meta->not_null
\tnumeric:      $meta->numeric
\tprimary_key:  $meta->primary_key
\ttable:        $meta->table
\ttype:         $meta->type
\tunique_key:   $meta->unique_key
\tunsigned:     $meta->unsigned
\tzerofill:     $meta->zerofill
";
}
$t_stop = microtime(true);
$t_proc = $t_stop - $t_start;
echo "processing time query 1: ".number_format($t_proc * 1000, 3)." ms\n";
unset($t_start);
unset($t_stop);
unset($t_proc);
$t_start = microtime(true);
$sql = mysql_query("DESCRIBE `table`");
while ($res = mysql_fetch_array($sql, MYSQL_ASSOC)) {
    print_r($res);
}
$t_stop = microtime(true);
$t_proc = $t_stop - $t_start;
echo "processing time query 2: ".number_format($t_proc * 1000, 3)." ms\n";
?>

Query 1 => 0.444 ms
Query 2 => 1.146 ms

So for easy usage, Query 2 is advised... But if your a performance-geek, you should use Query 1.

down

-1

mwwaygoo AT hotmail DOT com ¶

12 years ago

Using mysql_fetch_field you can produce a more robust version of mysql_fetch_assoc.



When querying 2 tables with the same field names, generally you would need to use mysql_fetch_row to get an integer key'ed array rather than an associated key'ed array. This is because fields of the same name in the second table will over-write the data returned from the first table.

However this simple function will insert the table name prior to the field name for the key and prevent cross-overs.



ie SELECT *, 'test' AS test 4 FROM table AS T_1, table AS T_2 WHERE T_1.a=T_2.b



could produce:



mysql_fetch_assoc() returns

array(

'index'=>2,

'a'=>'pear',

'b'=>'apple',

'test'=>'test',

4=>4

)



mysql_fetch_table_assoc() returns

array(

'T_1.index' =>1,

'T_1.a'=>'apple',

'T_1.b'=>'banana',

'T_2.index'=>2,

'T_2.a'=>'pear',

'T_2.b'=>'apple',

'test'=>'test',

4=>4

)



<?php

function mysql_fetch_table_assoc($resource)

{

    // function to get all data from a query, without over-writing the same field

    // by using the table name and the field name as the index

    

    // get data first

    $data=mysql_fetch_row($resource);

    if(!$data) return $data; // end of data

    

    // get field info

    $fields=array();

    $index=0;

    $num_fields=mysql_num_fields($resource);

    while($index<$num_fields)

    {

        $meta=mysql_fetch_field($resource, $index);

        if(!$meta)

        {

            // if no field info then just use index number by default

            $fields[$index]=$index;

        }

        else

        {

            $fields[$index]='';

            // deal with field aliases - ie no table name (SELECT T_1.a AS temp)

            if(!empty($meta->table)) $fields[$index]=$meta->table.'.';

            // deal with raw data - ie no field name (SELECT 1)

            if(!empty($meta->name))  $fields[$index].=$meta->name; else $fields[$index].=$index;

        }

        $index++;

    }

    $assoc_data=array_combine($fields, $data);

    return $assoc_data;

}

?>

down

-1

jorachim at geemail dot com ¶

16 years ago

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.

down

-2

Jonathan ¶

14 years ago

It should be noted that the primary_key member variable is only set to 1 if the primary key on the table is only on that 1 field. If you have a table that has a multiple column primary key, then you will not get what you might expect.

For example:
CREATE TABLE `line_item_table` (
  `liForeignKey1` int(11) unsigned not null,
  `liForeignKey2` int(11) unsigned not null,
  PRIMARY KEY (`liForeignKey1`, `liForeignKey2`)
) ENGINE=MyISAM;

While you might expect that primary_key == 1 for both columns; var_dump() will show you that you get the following for both fields:
["primary_key"]=>int(0)

This is as of PHP 5.2.13 and MySQL 5.0.51

down

-3

Daniel B ¶

12 years ago

Simple function to display all data in a query...

function dumpquery($query) {
    $numfields = mysql_num_fields($query);
    echo '<table border="1" bgcolor="white"><tr>';
    for ($i = 0; $i<$numfields; $i += 1) {
        $field = mysql_fetch_field($query, $i);
        echo '<th>' . $field->name . '</th>';
    }
    echo '</tr>';
    while ($fielddata = mysql_fetch_array($query)) {
        echo '<tr>';
        for ($i = 0; $i<$numfields; $i += 1) {
            $field = mysql_fetch_field($query, $i);
            echo '<td>' . $fielddata[$field->name] . '</td>';
        }
        echo '</tr>';
    }
    echo '</table>';    
}

down

-3

TALU ¶

15 years ago

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 
    } 
?>

down

-3

php at brayra dot com ¶

22 years ago

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.

down

-2

php [spat] hm2k.org ¶

16 years ago

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);
}

?>

down

-5

eviltofu at gmail dot com ¶

13 years ago

MYSQLI_TYPE_BLOB indicates the field is a BLOB or a TEXT. I think you would need to check the blob value. If its true then it's a BLOB, otherwise it's a TEXT. Can someone confirm?

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