checked() │ WP 1.0.0

Used in checkbox and radio fields of the form. Made for convenience, checks two values and if they match, outputs the attribute checked='checked' for the current form field.

This is one of the helper functions for forms: checked(), disabled(), selected(), wp_readonly().

There is a space at the beginning of the line: " checked='checked'".

When comparing values, they are first cast to the same type (string), and then compared:

(string) $one === (string) $two

Thus, a non-exact match will still trigger, for example:

  • int 1 will be equal to string '1'.
  • true will be equal to 1 or '1'.
  • false will be equal to 0 or '0'.
  • etc.
Uses: __checked_selected_helper()
1 time — 0.000001 sec (speed of light) | 50000 times — 0.01 sec (speed of light) | PHP 7.3.12, WP 5.3.2

No Hooks.

Returns

String. Outputs to the screen:

  • checked='checked' — when the passed values are equal to each other
  • '' (empty string) — when the passed values are not equal.

If the third parameter ($echo) is set to false, the function will not output anything to the screen.

Usage

<?php checked( $checked, $current, $echo ); ?>
$checked(string/int/bool) (required)
First of the values being compared.
$current(string/int/bool)
Second of the values being compared. Not required to fill, you just need to check the presence of the first parameter.
Default: true
$echo(bool)
Output the result to the screen (true) or return for processing (false).
Default: true

Examples

0

#1 Demo

See what the function outputs depending on the input of different parameters.

checked( 1 );            //  checked='checked'
checked( 0 );            // ''

checked( '1' );          //  checked='checked'
checked( '0' );          // ''

checked( true );         //  checked='checked'
checked( false );        // ''
checked( false, false ); //  checked='checked'

checked( 1, '1' );      //  checked='checked'
checked( true, '1' );   //  checked='checked'
checked( true, 'str' ); // ''

checked( 2 );           // ''
checked( 'str' );       // ''
checked( array() );     // ''
checked( array(true) ); // ''
checked( array(1) );    // ''
0

#2 Example of using checked() in code 

<?php
// get the option from the database. The option value is an array.
$option = get_option('slug_option');

// Get the value of the option we need
$checked = $option['self-destruct'] ?? false; // either true or 1 is expected here
?>

<input name="slug_option[self-destruct]" value="1"<?php checked( $checked ); ?>/>
0

#3 Compare the PHP variant vs ``checked()

Option with `checked()

<input type="checkbox" name="options[postlink]" value="1"<?php checked( $options['postlink'] ); ?> >

Option with if()

<input type='checkbox' name='options[postlink]' value='1' <?php if ( 1 == $options['postlink'] ) echo 'checked="checked"'; ?> >
0

#4 Multiselect checkbox

For multiselect checkbox use array in checked function instead of simple value.

<?php $postlink = get_post_meta( $post->ID, 'postlink', true ); ?>

<input type="checkbox" name="postlink[]" value="1"
	<?php checked( in_array( $postlink, 1 ), 1 ) ?> />

<input type="checkbox" name="postlink[]" value="2"
	<?php checked( in_array( $postlink, 2 ), 1 ) ?> />

<input type="checkbox" name="postlink[]" value="3"
	<?php checked( in_array( $postlink, 3 ), 1 ) ?> />

Changelog

Since 1.0.0 Introduced.

checked() code WP 6.9.1

wp-includes/general-template.php 
function checked( $checked, $current = true, $display = true ) {
	return __checked_selected_helper( $checked, $current, $display, 'checked' );
}

form functions

Supporting (helper utility auxiliary)