wpdb::get_col( string|null $query = null, int $x = 0 ): array
- Since
- 0.71
- Source
wp-includes/class-wpdb.php:3139
Description
Executes a SQL query and returns the column from the SQL result.
If the SQL result contains more than one column, the column specified is returned.
If $query is null, the specified column from the previous SQL result is returned.
Compatibility
- WordPress
- since 0.71
- PHP
- 7.4–8.6-dev
- 6.7.7
- 6.8.8
- 6.9.7
- 7.0.4
- 7.1.0
Present in every tracked release (6.7.7 to 7.1.0), and compiles on PHP 7.4 through 8.6-dev.
Parameters
$querystring|nulloptional- SQL query. Defaults to previous query.Default:
null $xintoptional- Column to return. Indexed from 0. Default 0.Default:
0
Return value
array- Database query result. Array indexed from 0 by SQL result row number.
Performance profile
How much work a call to wpdb::get_col() 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
- Trivial
- Scaling
- Scales with input
- Instructions
- 7–24
- Plugin surface
- None
- Called by
- 0
Reaches the database via wpdb::get_col().
The body loops, so the work grows with what you pass in.
Executed per call on PHP 8.5, depending on the branch taken. The body compiles to 32.
Nothing here hands control to plugin code.
Nothing in core calls this; the cost is only what you spend yourself.
What it touches
- sqldatabase query
wpdb::get_col()this function does it
What one call costs · 3 distinct outcomes
One number would be a lie: the work depends on which branch runs. These are every distinct cost wpdb::get_col() can have, taken from its control-flow graph on PHP 8.5.
| When | Instructions | Calls it makes |
|---|---|---|
| always | 7–13 | none |
| always | 12–18 | ->query() |
| always | 16–24 | ->check_safe_collation(), ->query() |
Across PHP versions
Compiles the same on PHP 7.4, 8.1, 8.2, 8.3, 8.4, 8.5 and 8.6-dev: 32 instructions, 7–24 executed per call, 5 branches. The work does not change between versions.
An instruction is not a fixed amount of time, so a matching count is not necessarily the same speed; what it rules out is a difference in the work itself.
Uses · 3
- wpdb::check_safe_collation()Checks if the query is accessing a collation considered safe.
- wpdb::query()Performs a database query, using current database connection.
- wpdb::get_var()Retrieves one value from the database.
Source code
public function get_col( $query = null, $x = 0 ) { if ( $query ) { if ( $this->check_current_query && $this->check_safe_collation( $query ) ) { $this->check_current_query = false; } $this->query( $query ); } $new_array = array(); // Extract the column values. if ( $this->last_result ) { for ( $i = 0, $j = count( $this->last_result ); $i < $j; $i++ ) { $new_array[] = $this->get_var( null, $x, $i ); } } return $new_array; }Changelog
Introduced in 0.71. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
About this page
- Parsed data
- Generated from the wordpress-develop 7.1.0 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. - Corrections
- Something wrong on this page? Report it and it gets fixed in the next regeneration.