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

Compatibility

Present in every tracked release (6.7.7 to 7.1.0), and compiles on PHP 7.4 through 8.6-dev.

Parameters

$tablestring

Table name.

Return value

string|WP_Error

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

Performance profile

How much work a call to wpdb::get_table_charset() does, and what it touches: the algorithmic scaling, the Zend instruction count per call across PHP versions, the hooks it hands control to, and the core code that calls it. Measured from the compiled opcodes, not a stopwatch, so every number is identical on any machine running the same PHP version, and every function in core is ranked by cost.

Cost class

Heavy

Reaches the database via ->get_results().

Scaling

Scales with input

The body loops, so the work grows with what you pass in.

Instructions

14–74

Executed per call on PHP 8.5, depending on the branch taken. The body compiles to 133.

Plugin surface

1 hook

Third-party callbacks on 'pre_get_table_charset' run inside this call, and their cost is not bounded by anything here.

Called by

4

4 places in core call this, so the cost is paid more often than your own code shows.

What it touches

• hookthird-party callbacksapply_filters()called directly
• sqldatabase query->get_results()called directly

Further down the call graph this can also reach query, option, cache, serialize and transient. Those are the worst case, several calls deep and usually down an error path, not what a normal call pays.

What one call costs · 6 distinct outcomes

One number would be a lie: the work depends on which branch runs. These are every distinct cost wpdb::get_table_charset() can have, taken from its control-flow graph on PHP 8.5.

Hooks and filters fired · 1

One hook fires while wpdb::get_table_charset() runs, in this order:

1. 1
   apply_filters( pre_get_table_charset )filterline 3212 (+15 into the body)

   Filters the table charset value before the DB is checked.

Uses · 4

• apply_filters()Calls the callback functions that have been added to a filter hook.
• __()Retrieves the translation of $text.
• wpdb::get_results()Retrieves an entire SQL result set from the database (i.e., many rows).
• WP_Error::__construct()Initializes the error.

Used by · 4

• wpdb::check_safe_collation()Checks if the query is accessing a collation considered safe on the current version of MySQL.
• wpdb::get_col_charset()Retrieves the character set for the given column.
• wpdb::get_col_length()Retrieves the maximum string length allowed in a given column.
• wpdb::strip_invalid_text_from_query()Strips any invalid characters from the query.

Source code

View on Trac ↗View on GitHub ↗

3197	protected function get_table_charset( $table ) {3198		$tablekey = strtolower( $table );3199 3200		/**3201		 * Filters the table charset value before the DB is checked.3202		 *3203		 * Returning a non-null value from the filter will effectively short-circuit3204		 * checking the DB for the charset, returning that value instead.3205		 *3206		 * @since 4.2.03207		 *3208		 * @param string|WP_Error|null $charset The character set to use, WP_Error object3209		 *                                      if it couldn't be found. Default null.3210		 * @param string               $table   The name of the table being checked.3211		 */3212		$charset = apply_filters( 'pre_get_table_charset', null, $table );3213		if ( null !== $charset ) {3214			return $charset;3215		}3216 3217		if ( isset( $this->table_charset[ $tablekey ] ) ) {3218			return $this->table_charset[ $tablekey ];3219		}3220 3221		$charsets = array();3222		$columns  = array();3223 3224		$table_parts = explode( '.', $table );3225		$table       = '`' . implode( '`.`', $table_parts ) . '`';3226		$results     = $this->get_results( "SHOW FULL COLUMNS FROM $table" );3227		if ( ! $results ) {3228			return new WP_Error( 'wpdb_get_table_charset_failure', __( 'Could not retrieve table charset.' ) );3229		}3230 3231		foreach ( $results as $column ) {3232			$columns[ strtolower( $column->Field ) ] = $column;3233		}3234 3235		$this->col_meta[ $tablekey ] = $columns;3236 3237		foreach ( $columns as $column ) {3238			if ( ! empty( $column->Collation ) ) {3239				list( $charset ) = explode( '_', $column->Collation );3240 3241				$charsets[ strtolower( $charset ) ] = true;3242			}3243 3244			list( $type ) = explode( '(', $column->Type );3245 3246			// A binary/blob means the whole query gets treated like this.3247			if ( in_array( strtoupper( $type ), array( 'BINARY', 'VARBINARY', 'TINYBLOB', 'MEDIUMBLOB', 'BLOB', 'LONGBLOB' ), true ) ) {3248				$this->table_charset[ $tablekey ] = 'binary';3249				return 'binary';3250			}3251		}3252 3253		// utf8mb3 is an alias for utf8.3254		if ( isset( $charsets['utf8mb3'] ) ) {3255			$charsets['utf8'] = true;3256			unset( $charsets['utf8mb3'] );3257		}3258 3259		// Check if we have more than one charset in play.3260		$count = count( $charsets );3261		if ( 1 === $count ) {3262			$charset = key( $charsets );3263		} elseif ( 0 === $count ) {3264			// No charsets, assume this table can store whatever.3265			$charset = false;3266		} else {3267			// More than one charset. Remove latin1 if present and recalculate.3268			unset( $charsets['latin1'] );3269			$count = count( $charsets );3270			if ( 1 === $count ) {3271				// Only one charset (besides latin1).3272				$charset = key( $charsets );3273			} elseif ( 2 === $count && isset( $charsets['utf8'], $charsets['utf8mb4'] ) ) {3274				// Two charsets, but they're utf8 and utf8mb4, use utf8.3275				$charset = 'utf8';3276			} else {

Changelog

Introduced in 4.2.0. Unchanged from 6.7.7 through 7.1.0.

1. 6.7.7
2. 6.8.8
3. 6.9.7
4. 7.0.4
5. 7.1.0

Signature, return type and hooks compared across 5 parsed releases.

About this page

Parsed data

Generated from the wordpress-develop 6.7.7 tag, from src/wp-includes/class-wpdb.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.

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