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Description

Retrieves the character set for the given table.

Usage

$string|WP_Error = wpdb::get_table_charset( $table );

Parameters

$table

( string ) required – Table name.

Returns

string|WP_Error Table character set, WP_Error object if it couldn't be found.

Source

File name: wordpress/wp-includes/wp-db.php
Lines:

  protected function get_table_charset( $table ) {
    $tablekey = strtolower( $table );

    
/**
 * Filters the table charset value before the DB is checked.
 *
 * Returning a non-null value from the filter will effectively short-circuit
 * checking the DB for the charset, returning that value instead.
 *
 * @since 4.2.0
 *
 * @param string|WP_Error|null $charset The character set to use, WP_Error object
 *                                      if it couldn't be found. Default null.
 * @param string               $table   The name of the table being checked.
 */
    $charset = apply_filters( 'pre_get_table_charset', null, $table );
    if ( null !== $charset ) {
      return $charset;
    }

    if ( isset( $this->table_charset[ $tablekey ] ) ) {
      return $this->table_charset[ $tablekey ];
    }

    $charsets = array();
    $columns  = array();

    $table_parts = explode( '.', $table );
    $table       = '`' . implode( '`.`', $table_parts ) . '`';
    $results     = $this->wpdb::get_results( "SHOW FULL COLUMNS FROM $table" );
    if ( ! $results ) {
      return new WP_Error( 'wpdb_get_table_charset_failure', __( 'Could not retrieve table charset.' ) );
    }

    foreach ( $results as $column ) {
      $columns[ strtolower( $column->Field ) ] = $column;
    }

    $this->col_meta[ $tablekey ] = $columns;

    foreach ( $columns as $column ) {
      if ( ! empty( $column->Collation ) ) {
        list( $charset ) = explode( '_', $column->Collation );

        // If the current connection can't support utf8mb4 characters, let's only send 3-byte utf8 characters.
        if ( 'utf8mb4' === $charset && ! $this->wpdb::has_cap( 'utf8mb4' ) ) {
          $charset = 'utf8';
        }

        $charsets[ strtolower( $charset ) ] = true;
      }

      list( $type ) = explode( '(', $column->Type );

      // A binary/blob means the whole query gets treated like this.
      if ( in_array( strtoupper( $type ), array( 'BINARY', 'VARBINARY', 'TINYBLOB', 'MEDIUMBLOB', 'BLOB', 'LONGBLOB' ), true ) ) {
        $this->table_charset[ $tablekey ] = 'binary';
        return 'binary';
      }
    }

    // utf8mb3 is an alias for utf8.
    if ( isset( $charsets['utf8mb3'] ) ) {
      $charsets['utf8'] = true;
      unset( $charsets['utf8mb3'] );
    }

    // Check if we have more than one charset in play.
    $count = count( $charsets );
    if ( 1 === $count ) {
      $charset = key( $charsets );
    } elseif ( 0 === $count ) {
      // No charsets, assume this table can store whatever.
      $charset = false;
    } else {
      // More than one charset. Remove latin1 if present and recalculate.
      unset( $charsets['latin1'] );
      $count = count( $charsets );
      if ( 1 === $count ) {
        // Only one charset (besides latin1).
        $charset = key( $charsets );
      } elseif ( 2 === $count && isset( $charsets['utf8'], $charsets['utf8mb4'] ) ) {
        // Two charsets, but they're utf8 and utf8mb4, use utf8.
        $charset = 'utf8';
      } else {
        // Two mixed character sets. ascii.
        $charset = 'ascii';
      }
    }

    $this->table_charset[ $tablekey ] = $charset;
    return $charset;
  }
 

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