Mute specific Slack channels after hours, Unmute them during business hours...

slack.php

<?php

// cronjob:
// 0 8 * * * /usr/bin/php /path/to/file.php unmute > /dev/null 2>&1
// 0 18 * * * /usr/bin/php /path/to/file.php mute > /dev/null 2>&1
	
if ( 1 < $argc ) {
    $channels = array(
		'CHANNEL_ID',
    );

    $after_hours_mute = array (
		'CHANNEL_ID',
    );
	
	if ( 'mute' == $argv['1'] ) {
		$channels = array_merge( $channels, $after_hours_mute );
	}
	
	mute( implode( ',', $channels ) );
}

function mute( $channels ) {
    $ch = curl_init( 'https://slack.com/api/users.prefs.set' );
    $data = http_build_query([
        'token' => 'YOUR_PERSONAL_TOKEN', // from: https://api.slack.com/custom-integrations/legacy-tokens
		'prefs' => json_encode( array( 'muted_channels' => $channels ) ),
    ]);
    curl_setopt( $ch, CURLOPT_CUSTOMREQUEST, 'POST' );
    curl_setopt( $ch, CURLOPT_POSTFIELDS, $data );
    curl_setopt( $ch, CURLOPT_RETURNTRANSFER, true );
    curl_setopt( $ch, CURLOPT_SSL_VERIFYPEER, false );
    $result = curl_exec( $ch );
    curl_close( $ch);

    return $result;
}