Replacing mysql_fetch_field() for column metadata

mysql_fetch_field() belonged to PHP's original MySQL extension and returned metadata about columns in a result set. The extension was removed from PHP 7. Modern applications can use MySQLi result metadata or query MySQL's schema metadata directly.

Historical mysql_fetch_field()

<?php
// Historical only: mysql_* was removed from PHP 7.
$result = mysql_query('SELECT * FROM student');
$field = mysql_fetch_field($result);
echo $field->name;
?>

MySQLi: metadata for the result set

<?php
$result = $connection->query(
    'SELECT id, name, class, mark FROM student'
);

foreach ($result->fetch_fields() as $field) {
    echo htmlspecialchars($field->name) . ' - type code: ' . $field->type . '<br>';
}
?>

fetch_fields() returns field objects for the columns in the result. Properties include the column name, original table/name information, length, flags and a MySQL type code.

Table definition with SHOW FULL COLUMNS

SHOW FULL COLUMNS FROM student;

This is often clearer when your goal is to inspect nullability, type, collation, keys, defaults, privileges and extra attributes of a table.

PDO + INFORMATION_SCHEMA

<?php
$sql = 'SELECT COLUMN_NAME, COLUMN_TYPE, IS_NULLABLE, COLUMN_KEY, COLUMN_DEFAULT, EXTRA
        FROM INFORMATION_SCHEMA.COLUMNS
        WHERE TABLE_SCHEMA = :schema AND TABLE_NAME = :table
        ORDER BY ORDINAL_POSITION';
$stmt = $dbo->prepare($sql);
$stmt->execute([
    'schema' => 'sql_tutorial',
    'table' => 'student'
]);
$columns = $stmt->fetchAll(PDO::FETCH_ASSOC);
?>

The original page's field-detail purpose is preserved, but current code no longer depends on removed mysql_num_fields() or mysql_field_flags(). Continue with column counts, column names, column types, and column attributes.

Related tutorials

Field names · Field types · Field attributes · Number of fields · Student SQL dump

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Subhendu Mohapatra

Author & Instructor at plus2net

I write and maintain practical tutorials on Python, PHP, SQL, JavaScript, HTML, jQuery, and web development at plus2net. The tutorials focus on clear explanations, working examples, and code that readers can test and adapt while learning.

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