preg_replace("%(?<=[?&])$param=.+(&|$)%", '', $url);

$string = 'https://www.google.com/search?q=Metallica+Turn+The+Page&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a&channel=sb';

$string = preg_replace('~?.*~', '', $string);

print $string;

https://www.google.com/search

// REPLACE ALL OF THE PARAMS WITH DUMMY-PARAM
$string = 'https://www.google.com/search?q=Metallica+Turn+The+Page&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a&channel=sb';

$string = preg_replace('~[?&]K([A-Z0-9+%]+)=.+?(?=&|$)~i', '$1=DUMMY-PARAM', $string);

print "nn".$string;

// REPLACE ALL OF THE KEYS WITH DUMMY-KEY
$string = 'https://www.google.com/search?q=Metallica+Turn+The+Page&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a&channel=sb';

$string = preg_replace('~[?&]K[A-Z0-9+%]+=(.+?)(?=&|$)~i', 'DUMMY-KEY=$1', $string);

print "nn".$string;

// PULL OUT ALL KEYS/VALUES
$string = 'https://www.google.com/search?q=Metallica+Turn+The+Page&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a&channel=sb';

$string = preg_replace('~[?&]K([A-Z0-9+%]+)=(.+?)(?=&|$)~i', "n$1: $2", $string);

print "nn".$string;