<?php
$string = 'tekst <a href="test.pl/test?var1=a1&var2=B2">test.pl/test?var1=a1&var2=B2</a> test.pl/test?var1=a1&var2=B2 lorem ipsum
tekst <a href="www.test.pl/test?var1=a1&var2=B2 ">www.test.pl/test?var1=a1&var2=B2 </a> www.test.pl/test?var1=a1&var2=B2  lorem ipsum
tekst <a href="http://test.pl/test?var1=a1&var2=B2 ">http://test.pl/test?var1=a1&var2=B2 </a> http://test.pl/test?var1=a1&var2=B2  lorem ipsum
tekst <a href="http://www.test.pl/test?var1=a1&var2=B2">http://www.test.pl/test?var1=a1&var2=B2</a> http://www.test.pl/test?var1=a1&var2=B2 lorem ipsum';

    echo nl2br($string).'<hr>';

    $pattern = '/^(http|https|ftp)://';
    $pattern = '/(http:|www)[=.:\/?&a-zA-Z0-9]*/';
    echo nl2br(preg_replace($pattern,"<strong>\\0</strong>",$string));