<?php
 
function highlight_phrases($string, $phrases, $tag = 'strong')
{
	usort($phrases, function($a,$b){
	    return strlen($b)-strlen($a);
	});
	print_r($phrases);
    $pattern = '/' . implode("|", array_map(function ($x) { 
    	return preg_quote($x, '/'); 
    }, $phrases)) . '/i';
    echo "\n$pattern";
    return preg_replace($pattern, '<' . $tag . '>$0</' . $tag . '>', $string);
}
 
$phrases = ['iphone 7', 'iphone 7 plus'];
$s = "This is some text about the iPhone 7 and this i really a nice peace of engineering. We are now talking about the iPhone 7 Plus, which is very big!";
echo "\n" . highlight_phrases($s, $phrases);
 

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