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Last updated: Fri, 18 May 2012

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mysql_fetch_field

(PHP 4, PHP 5)

mysql_fetch_field — Liefert ein Objekt mit Feldinformationen aus einem Anfrageergebnis

Beschreibung

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

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

Parameter-Liste

Ergebnis

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 Der Feldoffset startet bei 0.

Rückgabewerte

Liefert ein object mit Feldinformationen. Die Eigenschaften des Objekts sind:

  • name - Feldname
  • table - Name der Tabelle zu der das Feld gehört
  • max_length - maximale Länge des Feldes
  • not_null - 1, wenn das Feld nicht NULL sein kann
  • primary_key - 1, wenn das Feld ein primary key ist
  • unique_key - 1, wenn das Feld ein unique key ist
  • multiple_key - 1, wenn das Feld ein non-unique key ist
  • numeric - 1, wenn das Feld vom Typ 'numeric' ist
  • blob - 1, wenn das Feld vom Typ 'BLOB' ist
  • type - der Typ des Feldes
  • unsigned - 1, wenn das Feld vorzeichenlos ist
  • zerofill - 1, wenn das Feld zero-filled ist

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 Felder */
$i = 0;
while ($i < mysql_num_fields($result)) {
    echo "Information für Feld $i:<br />\n";
    $meta = mysql_fetch_field($result, $i);
    if (!$meta) {
        echo "Keine Information 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: Feldnamen, die von dieser Funktion zurückgegeben werden, unterscheiden sich in der Groß-/Kleinschreibung.

Siehe auch



add a note add a note User Contributed Notes
mysql_fetch_field
inaxio
04-Nov-2005 04:34
just another option to get all enum|set values from table definition. values are stored into arrays using the same field name

$result = mysql_query("SHOW COLUMNS FROM [table_name]");
while($row = mysql_fetch_object($result)){
   if(ereg(('set|enum'), $row->Type)){
       eval(ereg_replace('set|enum', '$'.$row->Field.' = array', $row->Type).';');
   }
}
Nick Baicoianu
15-Sep-2005 08:18
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.
admin at str-atm dot com
12-Sep-2005 07:15
If you need to get separated field size you should use
this part of code (I also included a database request function):

!!!!! Take care of warped lines

----------------
// Function to call to perform a database request

<?
function sql_request($sql_query,$db_name)
  {
    global $rows_count;
    $db_link = mysql_connect("localhost","username","password")
or die("MySQL connect failed");
    @mysql_select_db($db_name) or
die("unable to select: $db_name");
    $query_answer = mysql_query($sql_query);
    $rows_count = mysql_num_rows($query_answer);
    mysql_close($db_link);
    return $query_answer;
  }

$editing_db = "mydb";
$editing_table = "mytable";

$query_answer = sql_request("SHOW FIELDS FROM $editing_table",$editing_db);
$i = 0;
while ($row = mysql_fetch_array($query_answer))
{
  $table_structure[$i][0] = $row['Field'];
  $first_parenthesis = strpos($row['Type'],"(");
  $last_parenthesis = strpos($row['Type'],")");
  if ($first_parenthesis AND $last_parenthesis)
  {
    $table_structure[$i][1] = substr($row['Type'],0,$first_parenthesis);
    $table_structure[$i][2] = substr($row['Type'],$first_parenthesis+1,
$last_parenthesis-$first_parenthesis-1);
  }
  if ($row[Key] == "PRI") $table_structure[$i][3] = 1;
  echo $i." ".$table_structure[$i][0]." ";
  echo $table_structure[$i][1]." ";
  echo $table_structure[$i][2]." ".$table_structure[$i][3]."<br>";
  $i++;
}
?>
Hope this will be usefull!

Andre Lebeuf
STR ATM and Terminals
cortalux at gmail dot com
23-Jun-2005 07:09
A far easier way of getting information upon an enum field, is this.

function enumget($field="",$table="") {
    $result=mysql_query("SHOW COLUMNS FROM `$table` LIKE '$field'");
    if(mysql_num_rows($result)>0){
        $row=mysql_fetch_row($result);
        $options=explode("','", preg_replace("/(enum|set)\('(.+?)'\)/","\\2", $row[1]));
    } else {
        $options=array();
    }
    return $options;
}
creak at foolstep dot com
18-Jul-2003 12:26
Sorry, the last pattern doesn't work with type whithout length, so it would be better if you change it with this one :
    "^([a-zA-Z]+)\(?([^\)]*)\)?$"

It's still $type[1] for the type and $type[2] for the length.

Creak
blakjak at nospam dot com
27-Mar-2003 11:18
mysql_fetch_field will fail if your result set's internal pointer has advanced past the end of the result.

So, if you use ...

$result = mysql_query("select * from person where id=1"); // returns 1 row
$row = mysql_fetch_row($result);

while($field = mysql_fetch_field){
 echo $field->name;
}

... you won't see any fields.  If you need to use mysql_fetch_field, you need to do it before you've iterated through all the rows in the result set.
kflam at awc dot net dot au
19-Jun-2002 05:56
#Input: the table name and the enum field
#Output: an array that stores all options of the enum field or
#false if the input field is not an enum
function getEnumOptions($table, $field) {
   $finalResult = array();

   if (strlen(trim($table)) < 1) return false;
   $query  = "show columns from $table";
   $result = mysql_query($query);
   while ($row = mysql_fetch_array($result)){
        if ($field != $row["Field"]) continue;
        //check if enum type
        if (ereg('enum.(.*).', $row['Type'], $match)) {
            $opts = explode(',', $match[1]);
            foreach ($opts as $item)
                $finalResult[] = substr($item, 1, strlen($item)-2);
        }
        else
                return false;
   }
   return $finalResult;
}

The function could be handy when making a selection option without typing all the options items respectively.
chrisshaffer at bellsouth dot net
06-Jun-2002 08:22
Slight error in the above comment:
$fieldLen = split("','",substr(1,-1,$fieldLen));

should read:
$fieldLen = split("','",substr($fieldLen,1,-1));

oops! ;)

I did take the above code (which saved me at least two hours worth of work), and massaged it into a function:

function mysql_enum_values($tableName,$fieldName)
{
  $result = mysql_query("DESCRIBE $tableName");

  //then loop:
  while($row = mysql_fetch_array($result))
  {
    //# row is mysql type, in format "int(11) unsigned zerofill"
    //# or "enum('cheese','salmon')" etc.

    ereg('^([^ (]+)(\((.+)\))?([ ](.+))?$',$row['Type'],$fieldTypeSplit);
    //# split type up into array
    $ret_fieldName = $row['Field'];
    $fieldType = $fieldTypeSplit[1];// eg 'int' for integer.
    $fieldFlags = $fieldTypeSplit[5]; // eg 'binary' or 'unsigned zerofill'.
    $fieldLen = $fieldTypeSplit[3]; // eg 11, or 'cheese','salmon' for enum.

    if (($fieldType=='enum' || $fieldType=='set') && ($ret_fieldName==$fieldName) )
    {
      $fieldOptions = split("','",substr($fieldLen,1,-1));
      return $fieldOptions;
    }
  }

  //if the funciton makes it this far, then it either
  //did not find an enum/set field type, or it
  //failed to find the the fieldname, so exit FALSE!
  return FALSE;

}

The most useful thing that I can think to do with this is to populate a HTML Dropdown box with it:

echo "<SELECT NAME=\"Select\" SIZE='1'>";
foreach($fieldOptions as $tmp)
{
  echo "<OPTION>$tmp";
}

Hope this helps  :D
justin at quadmyre dot com
19-Apr-2002 02:00
Same problem, slightly different solution.

$result = mysql_query("DESCRIBE tablename");
# or SHOW COLUMNS FROM
# or SHOW FIELDS FROM

then loop:

$row = mysql_fetch_array($result);
# row is mysql type, in format "int(11) unsigned zerofill"
# or "enum('cheese','salmon')" etc.

ereg('^([^ (]+)(\((.+)\))?([ ](.+))?$',$row['Type'],$fieldTypeSplit);
# split type up into array

$fieldType = $fieldTypeSplit[1]; # eg 'int' for integer.
$fieldFlags = $fieldTypeSplit[5]; # eg 'binary' or 'unsigned zerofill'.
$fieldLen = $fieldTypeSplit[3]; # eg 11, or 'cheese','salmon' for enum.

You might then like to:

if ($fieldType=='enum' or $fieldType=='set')
  $fieldLen = split("','",substr(1,-1,$fieldLen));

So for enum or set types, $fieldLen becomes an array of possible values.

Hope that helps someone out there...
php at brayra dot com
22-Mar-2002 01:09
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:
$myfields = GetFieldInfo('test_table');
print "<pre>";
print_r($myfields);
print "</pre>";

The field objects now have 'len', 'values' and 'flags' parameters.
NOTE: 'values' only has data for set and enum fields.

//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 03:12
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....

$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'];
}
dave at techweavers dot net
04-Oct-2000 10:48
If you want to get the max length of a column not just the data use this:
$result = mysql_query ("SELECT * FROM table");
$fields = mysql_num_fields ($result);
$i = 0;
while ($i < $fields) {
$len   = mysql_field_len   ($result, $i);
$i++;
}
Or refer to http://www.php.net/manual/function.mysql-field-type.php
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mysql_fetch_lengths> <mysql_fetch_assoc
Last updated: Fri, 18 May 2012