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mysql_num_fields

(PHP 4, PHP 5)

mysql_num_fieldsGet number of fields in result

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_num_fields(resource $result): int|false

Retrieves the number of fields from a query.

Elenco dei parametri

result

The risultato resource che che viene calcolato. Questo risultato deriva dal una chiamata a mysql_query().

Valori restituiti

Returns the number of fields in the result set resource on success o false in caso di fallimento.

Esempi

Example #1 A mysql_num_fields() example

<?php
$result
= mysql_query("SELECT id,email FROM people WHERE id = '42'");
if (!
$result) {
echo
'Could not run query: ' . mysql_error();
exit;
}

/* returns 2 because id,email === two fields */
echo mysql_num_fields($result);
?>

Note

Nota:

Per la compatibilità all'indietro, i seguenti sinonimi (deprecati) possono essere utilizzati: mysql_numfields()

Vedere anche:

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User Contributed Notes 5 notes

up
0
php at jezusisheer dot nl
17 years ago
Note that, if you want to get the amount of columns of a table and you're using the "SHOW COLUMNS FROM $table" query, you will have to use mysql_num_rows() instead of mysql_num_fields() on the result. This becomes logical when thinking about it, because the SHOW COLUMNS query returns a result with six columns (Field, Type, Null, Key, Default and Extra) and with a single row for every column found. If you'd count the number of fields, you'd always get 6. If you count the number of rows, you'll get the amount of columns found.
up
-2
matt at iwdt dot net
22 years ago
here's one way to print out a row of <th> tags from a table
NOTE: i didn't test this

$result = mysql_query("select * from table");

for ($i = 0; $i < mysql_num_fields($result); $i++) {
print "<th>".mysql_field_name($result, $i)."</th>\n";
}

post a comment if there's an error
up
-6
tharkey at tharkey dot net
20 years ago
You can use it without a requete, just to list the fields :

$liste_champs = mysql_list_fields ( $Base, $Table, $connexion);

for ($i=0; $i < mysql_num_fields ($l_champs); $i++) {
echo ( mysql_field_name ($l_champs, $i) );
echo (' / ');
}
up
-5
bwark at stanford dot edu
23 years ago
If you just want the number of fields in a table, you can do something like this:

<?php
$db_id
= mysql_connet();
$result = mysql_query("DESCRIBE [tableName], $db_id);

$numFields = mysql_num_rows($result);
?>

Because "
DESCRIBE" returns one row for each field in the table (at least in MySQL), this will work.
up
-12
apass AT passmoore DOT com
21 years ago
Adding to the last comment: you can dynamically loop through any number of columns AND rows like so-

$query="your SQL";
$result=mysql_query($query) or die("Query ($query) sucks!");
$fields=mysql_num_fields($result);

echo "<table>\n<tr>";
for ($i=0; $i < mysql_num_fields($result); $i++) //Table Header
{ print "<th>".mysql_field_name($result, $i)."</th>"; }
echo "</tr>\n";
while ($row = mysql_fetch_row($result)) { //Table body
echo "<tr>";
for ($f=0; $f < $fields; $f++) {
echo "<td>$row[$f]</td>"; }
echo "</tr>\n";}
echo "</table><p>";

This has been tested.
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