PHP weighted link rotators

weigted-link-rotator.php

<?php
/**
 * File: weighted-link-rotator.php
 *
 * This is a simple implementation of weighted link rotator. PHP weighted link rotator is a code to display one link chosen randomly
 * from a list of URLs. However each URL has a weighted probability. A URL may have a bigger chance to be displayed when it has bigger
 * probability. 
 */

/**
 * Get a link with calculating its weighted probability.
 * 
 * @param array $links array of URLs, 2D array in with the child array has url and weight as the key.
 * 
 * @return string|bool the chosen url or return false if $links is empty array or no URL is found. 
 */
function get_link_to_display( $links )  {
    if( empty( $links ) ) {
        	return false;
	}
    
	// Generate a random number between 1 to 100. 
	$rand_num = mt_rand( 1, 100 );

	// Filter only elements that has weight above the $rand_num
	$filtered_arr = array_filter( $links, function( $val ) use ( $rand_num ) {
    	return ( $rand_num < $val['weight'] );
	});

	// Get the chosen one that is the first element of the filtered array.
	$chosen = current( $filtered_arr );
	
	if (empty( $chosen ) or ! isset( $chosen['url'] ) ) {
	    return false;
	}

	// Show the URL.
	return urldecode( $chosen['url'] );
}

// Sample data.
$links   = array();
$links[] = array( 
    'id'     => 'linkA',
    'url'    => 'https://www.google.com/imgres?imgurl=https%3A%2F%2Fimage.shutterstock.com%2Fimage-photo%2Fmountains-under-mist-morning-amazing-260nw-1725825019.jpg&imgrefurl=https%3A%2F%2Fstocksnap.io%2Fsearch%2Fnature&tbnid=ez-ubljHwN9MSM&vet=12ahUKEwiqwp3OyqjwAhVRs0sFHUljCBgQMygBegUIARDTAQ..i&docid=JEwZUI4DSxP5DM&w=390&h=280&q=images&safe=strict&ved=2ahUKEwiqwp3OyqjwAhVRs0sFHUljCBgQMygBegUIARDTAQ',
    'weight' => 20, 
);
$links[] = array( 
    'id'     => 'linkB',
    'url'    => 'https://www.google.com/imgres?imgurl=https%3A%2F%2Fcdn.pixabay.com%2Fphoto%2F2015%2F04%2F23%2F22%2F00%2Ftree-736885__480.jpg&imgrefurl=https%3A%2F%2Fpixabay.com%2Fimages%2Fsearch%2Fnature%2F&tbnid=GEQYC6WSjtkqBM&vet=12ahUKEwiqwp3OyqjwAhVRs0sFHUljCBgQMygDegUIARDXAQ..i&docid=Ba_eiczVaD9-zM&w=771&h=480&q=images&safe=strict&ved=2ahUKEwiqwp3OyqjwAhVRs0sFHUljCBgQMygDegUIARDXAQ',
    'weight' => 40, 
);
$links[] = array( 
    'id'     => 'linkC',
    'url'    => 'https://www.google.com/imgres?imgurl=https%3A%2F%2Fimages.ctfassets.net%2Fhrltx12pl8hq%2F4plHDVeTkWuFMihxQnzBSb%2Faea2f06d675c3d710d095306e377382f%2Fshutterstock_554314555_copy.jpg&imgrefurl=https%3A%2F%2Fwww.shutterstock.com%2Fdiscover%2F10-free-stock-images&tbnid=1Y5Fex7Bw6VMkM&vet=12ahUKEwiqwp3OyqjwAhVRs0sFHUljCBgQMygIegUIARDiAQ..i&docid=YAMnwpTKFlPEWM&w=2500&h=1227&q=images&safe=strict&ved=2ahUKEwiqwp3OyqjwAhVRs0sFHUljCBgQMygIegUIARDiAQ',
    'weight' => 60, 
);
$links[] = array( 
    'id'     => 'linkD',
    'url'    => 'https://www.google.com/imgres?imgurl=https%3A%2F%2Fmedia.istockphoto.com%2Fphotos%2Fchild-hands-formig-heart-shape-picture-id951945718%3Fk%3D6%26m%3D951945718%26s%3D612x612%26w%3D0%26h%3Dih-N7RytxrTfhDyvyTQCA5q5xKoJToKSYgdsJ_mHrv0%3D&imgrefurl=https%3A%2F%2Fwww.istockphoto.com%2Fphotos%2Fpeace-maker&tbnid=1E4Z16ujrn_JRM&vet=12ahUKEwiqwp3OyqjwAhVRs0sFHUljCBgQMygGegUIARDdAQ..i&docid=27q4HQp-2Qmx0M&w=612&h=346&q=images&safe=strict&ved=2ahUKEwiqwp3OyqjwAhVRs0sFHUljCBgQMygGegUIARDdAQ',
    'weight' => 80, 
);
$links[] = array( 
    'id'     => 'linkE',
    'url'    => 'https://www.google.com/imgres?imgurl=https%3A%2F%2Fcdn.pixabay.com%2Fphoto%2F2019%2F02%2F15%2F11%2F04%2Fbook-3998252__340.jpg&imgrefurl=https%3A%2F%2Fpixabay.com%2Fimages%2Fsearch%2Fweekend%2F&tbnid=hS9EDD38WRmkxM&vet=12ahUKEwiqwp3OyqjwAhVRs0sFHUljCBgQMygNegUIARDsAQ..i&docid=X9Ts63vD-KMxXM&w=510&h=340&q=images&safe=strict&ved=2ahUKEwiqwp3OyqjwAhVRs0sFHUljCBgQMygNegUIARDsAQ',
    'weight' => 90, 
);
$links[] = array( 
    'id'     => 'linkF',
    'url'    => 'https://www.google.com/imgres?imgurl=https%3A%2F%2Fstatic.toiimg.com%2Fphoto%2F72975551.cms&imgrefurl=https%3A%2F%2Ftimesofindia.indiatimes.com%2Flife-style%2Fevents%2Fsurya-grahan-today-annular-solar-eclipse-2019-december-images-photos-pics-video-check-out-these-breathing-pictures-of-the-seasons-last-surya-grahan-of-26-december-2019-india%2Fphotostory%2F72975550.cms&tbnid=pTd2OIa33-6LVM&vet=12ahUKEwiqwp3OyqjwAhVRs0sFHUljCBgQMygRegUIARD0AQ..i&docid=78aIM0GrmvG9rM&w=1200&h=900&q=images&safe=strict&ved=2ahUKEwiqwp3OyqjwAhVRs0sFHUljCBgQMygRegUIARD0AQ',
    'weight' => 100, 
);

// The displayed link.
echo get_link_to_display( $links );