checked() │ WP 1.0.0

Outputs the html checked attribute.

Compares the first two arguments and if identical marks as checked.

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.

Return

String. HTML attribute or empty string.

Usage

checked( $checked, $current, $display );
$checked(mixed) (required)
One of the values to compare.
$current(mixed)
The other value to compare if not just true.
Default: true
$display(true|false)
Whether to echo or just return the string.
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( 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 6.5.2

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)