mysql_fetch_field

(PHP 4, PHP 5)

mysql_fetch_field Ottiene informazioni sulla colonna da un risultato e le restituisce come oggetto

Descrizione

object mysql_fetch_field ( resource $risultato [, int $ indice_campo ] )

Restituisce un oggetto contenente le informazioni di un campo.

mysql_fetch_field() può essere usata al fine di ottenere informazioni circa i campi di un determinato risultato di una query. Se l'indice del campo non è specificato, il successivo campo non ancora recuperato da mysql_fetch_field() viene considerato.

Le proprietà dell'oggetto sono:

  • name - nome della colonna
  • table - nome della tabella a cui appartiene la colonna
  • max_length - massima lunghezza della colonna
  • not_null - 1 se la colonna non può essere NULL
  • primary_key - 1 se la colonna è una chiave primaria
  • unique_key - 1 se la colonna è una chiave unica
  • multiple_key - 1 se la colonna è una chiave non-unica
  • numeric - 1 se la colonna è numerica
  • blob - 1 se la colonna è un BLOB
  • type - il tipo della colonna
  • unsigned - 1 se la colonna è senza segno
  • zerofill - 1 se la colonna è completata da zeri

Example #1 mysql_fetch_field()

<?php
mysql_connect
('localhost:3306'$utente$password)
    or die(
"Connessione non riuscita: " mysql_error());
mysql_select_db("database");
$risultato mysql_query("select * from tabella")
    or die(
"Query fallita: " mysql_error());
/* ottiene i metadata della colonna */
$i 0;
while (
$i mysql_num_fields($risultato)) {
    echo 
"Informazioni della colonna $i:<br />\n";
    
$meta mysql_fetch_field($risultato);
    if (!
$meta) {
        echo 
"Nessuna informazione disponibile<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>"
;
    
$i++;
}
mysql_free_result($risultato);
?>

Vedere anche mysql_field_seek().

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User Contributed Notes 13 notes

up
4
krang at krang dot org dot uk
12 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'];
}
?>
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2
lucien at ocia dot nl
2 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.
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2
mwwaygoo AT hotmail DOT com
2 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;
}
?>
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1
eviltofu at gmail dot com
3 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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0
Daniel B
2 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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0
Jonathan
4 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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0
TALU
5 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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0
php [spat] hm2k.org
5 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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0
jorachim at geemail dot com
5 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.
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0
david at vitam dot be
6 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;
}
?>
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0
dheep
6 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++;
}
?>

OUTPUt:
0.id
1.todo
2.due date
3.priority
4.type
5.status
6.notes

hope this is useful.
up
0
Nick Baicoianu
9 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.
up
0
php at brayra dot com
12 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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