<?php
 
    function properCase( $string ) {	
		$ignorar = array( 'do', 'dos', 'da', 'das', 'de' );
		$array = explode(' ', strtolower( $string ) );
		$out = '';
		foreach ($array as $ar) {
           $out .= ( in_array ( $ar, $ignorar ) ? $ar : ucfirst( $ar ) ).' ';
		}
		return trim( $out );
    }
 
	echo properCase( 'DEPARTAMENTO DE GALINHAS' ).PHP_EOL;
	echo properCase( 'HOSPITAL DOS PLANTADORES DE CANA' ).PHP_EOL;
	echo properCase( 'rua do descalço' ).PHP_EOL;
 

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