mysql_fetch_field

(PHP 4, PHP 5)

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

Avviso

Questa enstensione deprecata da PHP 5.5.0, e sarà rimossa in futuro. Al suo posto, usare l'estensione MySQLi o PDO_MySQL. Vedere anche la guida MySQL: scelta dell'API e le FAQ relative per ulteriori informazioni. Le alternative a questa funzione includono:

Descrizione

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

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

Elenco dei parametri

result: The risultato resource che che viene calcolato. Questo risultato deriva dal una chiamata a 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.

Valori restituiti

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

name - column name
table - name of the table the column belongs to, which is the alias name if one is defined
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

Esempi

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
unique_key:   $meta->unique_key
unsigned:     $meta->unsigned
zerofill:     $meta->zerofill
</pre>";
    $i++;
}
mysql_free_result($result);
?>

Note

Nota: I nomi dei campi restituiti da questa funzione sono case-sensitive.

Nota:
If field or tablenames are aliased in the SQL query the aliased name will be returned. The original name can be retrieved for instance by using mysqli_result::fetch_field().

Vedere anche:

mysql_field_seek() - Set result pointer to a specified field offset

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User Contributed Notes 13 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

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

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

-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

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-2

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

-2

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

-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>';    
}

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-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 
    } 
?>

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-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);
}

?>

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-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.

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-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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-5

dheep ¶

16 years ago


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++;

}

?>



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hope this is useful.

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