mysql_num_fields

(PHP 4, PHP 5)

mysql_num_fields — Get 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:

mysql_select_db() - Select a MySQL database
mysql_query() - Send a MySQL query
mysql_fetch_field() - Get column information from a result and return as an object
mysql_num_rows() - Get number of rows in result

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User Contributed Notes 3 notes

down

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.

down

-2

matt at iwdt dot net ¶

23 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

down

-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.

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