describe_table()

public function describe_table(string $table, bool $names_only = false): array|bool

Description

Retrieves structural information about a database table using MySQL's DESCRIBE statement. This method can return either detailed column information or just column names. It's useful for dynamic form generation, validation, and understanding table schema at runtime.

Parameters

Parameter	Type	Description	Default	Required
table	string	The name of the table to describe.	-	Yes
names_only	bool	If true, returns only column names. If false, returns full column details.	false	No

Return Value

Type	Description
array\|bool	Returns array of column details/names on success, or false on failure (e.g., table doesn't exist).

Column Details Structure

When $names_only = false, each array element contains these keys:

Key	Description	Example Value
Field	Column name	'id', 'username', 'email'
Type	Data type with length/precision	'int(11)', 'varchar(255)', 'decimal(10,2)'
Null	Whether NULL values are allowed ('YES' or 'NO')	'NO', 'YES'
Key	Index information (PRI, UNI, MUL, or empty)	'PRI', 'UNI', 'MUL', ''
Default	Default value or NULL	'NULL', 'CURRENT_TIMESTAMP', '0'
Extra	Additional information (auto_increment, etc.)	'auto_increment', ''

Example #1: Getting Full Column Details

The code sample below demonstrates how to retrieve complete column information from the 'users' table.

PHP

$columns = $this->db->describe_table('users');

if ($columns !== false) {
    foreach ($columns as $column) {
        echo "Column: " . $column['Field'] . "";
        echo "Type: " . $column['Type'] . "";
        echo "Primary Key: " . ($column['Key'] === 'PRI' ? 'Yes' : 'No') . "";
        echo "Nullable: " . $column['Null'] . "";
        echo "Default: " . ($column['Default'] ?? 'None') . "";
        echo "Extra: " . ($column['Extra'] ?? 'None') . "";
    }
} else {
    echo "Failed to describe table or table doesn't exist.";
}

Example #2: Getting Only Column Names

The code sample below demonstrates how to retrieve just the column names from the 'products' table.

PHP

$column_names = $this->db->describe_table('products', true);

if ($column_names !== false) {
    echo "Columns in 'products' table:";
    echo implode(', ', $column_names);
    
    // Can be used for dynamic form generation
    foreach ($column_names as $column) {
        if ($column !== 'id') { // Skip ID field
            echo '<input type="text" name="' . $column . '" placeholder="' . $column . '">';
        }
    }
} else {
    echo "Table 'products' not found.";
}

Example #3: Using Column Information for Validation

The code sample below demonstrates how to use column information to validate data before insertion.

PHP

// Get column details
$column_details = $this->db->describe_table('orders');

if ($column_details !== false) {
    $data_to_insert = [
        'customer_id' => 123,
        'total_amount' => 99.99,
        'order_date' => date('Y-m-d H:i:s')
    ];
    
    // Check if all columns in data exist in table
    foreach (array_keys($data_to_insert) as $column) {
        $column_exists = false;
        foreach ($column_details as $col_detail) {
            if ($col_detail['Field'] === $column) {
                $column_exists = true;
                break;
            }
        }
        
        if (!$column_exists) {
            echo "Error: Column '$column' doesn't exist in 'orders' table.";
        }
    }
}

Important Notes

The $table parameter is required.
Returns false on failure (e.g., table doesn't exist, database error).
Uses MySQL's DESCRIBE statement which is MySQL-specific (not portable to other databases).
When $names_only = true, returns a simple indexed array of column names.
When $names_only = false, returns an array of associative arrays with column details.
Useful for dynamic applications that need to adapt to different table structures.
Consider caching results if calling frequently on the same table.
For more detailed metadata, consider using SHOW FULL COLUMNS FROM or querying INFORMATION_SCHEMA directly.