<?php
 
$array = array('s00473276\Soul To Squeeze\Red Hot Chili Peppers',
               't00034422\Soul To Squeeze\Red Hot Chili Peppers',
               '209676\Soul To Squeeze\Red Hot Chili Peppers',
               's00473331\What Is Soul ?\Red Hot Chili Peppers',
               '209672\Show Me Your Soul\Red Hot Chili Peppers',
               't00034415\Show Me Your Soul\Red Hot Chili Peppers',
               's00473268\Show Me Your Soul\Red Hot Chili Peppers',
);
 
function myFunc($item) {
	$parts = explode('\\', $item, 2);
 
	return $parts[0];
}
 
$newArray = array_map('myFunc', $array);
 
print_r($newArray);

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