' . $matches[3] . $matches[4]; endif; return $matches[0]; }, $content ); return $content; } add_filter( 'the_content', 'auto_id_headings' );"> ' . $matches[3] . $matches[4]; endif; return $matches[0]; }, $content ); return $content; } add_filter( 'the_content', 'auto_id_headings' );"> ' . $matches[3] . $matches[4]; endif; return $matches[0]; }, $content ); return $content; } add_filter( 'the_content', 'auto_id_headings' );"> 
/**
 * Automatically add IDs to headings such as <h2></h2>
 */
function auto_id_headings( $content ) {

	$content = preg_replace_callback( '/(\\<h[1-6](.*?))\\>(.*)(<\\/h[1-6]>)/i', function( $matches ) {
		if ( ! stripos( $matches[0], 'id=' ) ) :
			$matches[0] = $matches[1] . $matches[2] . ' id="' . sanitize_title( $matches[3] ) . '">' . $matches[3] . $matches[4];
		endif;
		return $matches[0];
	}, $content );

    return $content;

}
add_filter( 'the_content', 'auto_id_headings' );

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